At first, when Peyton Manning woke up from the anesthesia, he was relieved: The pain in the neck that he had lived with for years was gone. As he came to, he stirred in the hospital bed, took stock of his misery-free condition, and started to push himself upright. Then it happened — his right arm buckled beneath him. Surprised, he struggled again to sit up, and at that moment, he understood his career was in jeopardy.

It was May 2011, and Manning had checked into Northwestern Memorial Hospital in Chicago for surgery on a herniated disc, a tear in the protective ring in his neck that had undermined his performance after 14 seasons with the Indianapolis Colts. The procedure was supposed to fix it, but now when he pushed himself up in bed, his right triceps was unable to bear his weight. Trying to contain his alarm, the most eminent quarterback in the NFL asked his surgeon what had happened to his arm. The surgeon explained that the disc had been pressing on a nerve. It would take some time for the irritation to subside, and for the nerve and muscle to come back alive.

But two weeks later, Manning’s arm still felt weak. By this time he noticed that the grip strength in his hand also appeared to be affected. “If any other part of your body has some weakness you go, ‘Well I can probably manage,’” Manning says. “But when you’re a quarterback and it’s your right hand, you’re certainly concerned far as being able to do your job.” His doctors discovered that he had re-herniated the disc, and Manning returned to the hospital for a second surgery, this one in virtual secrecy.

While he waited to heal, Manning largely disappeared from public view, unwilling to let anyone see his arm in such feeble condition. “I wasn’t just going to throw with anybody around watching,” he says. “I was guarded and protective.” The NFL was in the midst of a four-month labor lockout, which meant he couldn’t use the Colts’ facilities or trainers, so he looked for a place to rehab unobserved. His old college friend Todd Helton, then a first baseman with the Colorado Rockies, suggested he come out to Denver where he could work out secretly and get treatment from the Rockies’ trainers, who were accustomed to dealing with arms.

The first pass Manning threw post-surgery was to Helton, and they were so concerned with privacy that they went to an underground batting cage beneath the Rockies’ stadium. Helton took up a position about 10 yards away and held out his hands. Manning reared back, and threw.

The Post Sports Live crew discusses how new information about Peyton Manning's injury changes how we view his legacy and previews Mike Shanahan's return to Denver. (Post Sports Live/The Washington Post)

“The ball nose-dived after about five yards,” Manning says.

It didn’t even make it halfway to Helton before it hit the ground. Helton burst out laughing — he thought Manning was joking.

“C’mon, quit kidding,” he said.

“Man, I wish I was,” Manning said.

‘I had to relearn’ how to throw

It’s always been an interesting question what Peyton Manning was given and what he acquired for himself. At this point, 37 years old, with a zipper scar on his neck, stoop-shouldered and slack-armed compared to his youth, it’s safe to conclude that his inherited genetic gifts are the least of him. Even in shoulder pads he is lank and relatively unmuscled next to younger specimens, and with his shirt off, well, he’s no Gatorade commercial.

The upper body atrophied after three surgeries cost him the 2011 season and his job with the Colts, leaving him with that strip of stitches as if Zorro tried to cut his shirt off at the collar. Yet somehow a man with two soldered together vertebrae enters Sunday's game against the Washington Redskins playing the best football of his life and maybe of any NFL quarterback ever: He has led the Denver Broncos to a 6-1 record and is on pace to set single-season records for touchdowns, yardage and completion percentage.

All of which makes it difficult to conceive that just 18 months ago Manning wondered whether he would ever play again — the only reminders an occasional pass that shows a telltale wobble, and dies.

“I don’t believe I throw quite the same as before I was injured,” Manning says by phone on his way home from a recent Broncos practice. “A lot of that is injury, a lot of it is being 37 years old, and a lot is playing with a new team. I’ve had a lot of change. It’s hard to know what percentage is what. I’m just trying to be the best player I can be in this new chapter.”

Cut by Indianapolis post-surgery, it seemed victory enough when Manning made it back to the field in a Broncos uniform last season and led them to a 13-3 record. But those closest to him say the feat was if anything underestimated. “I don’t think people really understand what he overcame,” says Duke head coach David Cutcliffe, Manning’s offensive coordinator at the University of Tennessee. According to Manning’s father Archie, he was closer to retirement than anyone knew.

“It was, ‘Am I gonna throw like a 40-year-old man?’ He didn’t want to be out there if he didn’t belong,” Archie says.

It’s a fact Manning candidly admits, and for the first time discusses without reserve. That he underwent neck surgeries was well-known — it was “a public ordeal,” as he puts it — but what he hasn’t talked about freely until now was just how weak the arm was and how far he had to go to recover it. The surgeries so reduced him that when he began rehabilitation, he could barely grip the ball. “I had to relearn,” he says. And in the relearning, he learned some things about himself. For one, he says, “That I could persevere.”

Manning was born with undeniable gifts, a tangle of ribonucleic acids that bestowed on him golden boyness, a scanning intelligence, and that python-thick arm he got from his cool and silvery old man Archie, who remains a legend at Ole Miss and quarterbacked the New Orleans Saints from 1971 to 1982.

But Manning was also born with a congenital weakness: that neck. He was 16 when his older brother Cooper, a promising wide receiver, received a diagnosis of career-ending spinal stenosis, a collapsing of the spaces between his vertebrae that pressured the spinal cord. Archie insisted his younger sons Peyton and Eli be thoroughly examined for spinal-cervical weakness, too, and a doctor pronounced teenaged Peyton’s neck curvature a potential problem. It wasn’t bad enough to forbid football, but it was less than ideal.

“Not picture perfect,” Manning says.

For 20 years, the golden boyness trumped the not-picture-perfect flaw. Between the ages of 15 and 35, he never missed a game with an injury. He made every start for 14 seasons with the Colts, winning four most valuable player awards, and a Super Bowl after the 2006 season. “I’d had this string of good health and good fortune,” he says. “Good protection, good coaches, good linemen, played in a good system. When you play for 20 years, and really, I never had to miss a game due to injury, that’s not just good protection. That’s good luck.”

But then the neck began to fray. He developed a pinched nerve, for which he underwent surgery in February 2010. Then came the herniated disc and successive surgeries in 2011.

There was no blueprint for nerve regeneration, Manning’s doctors told him. Sometimes nerves came back 100 percent, and sometimes they came back at 50 percent. And sometimes they didn’t recover at all. There was no timetable, or treatment, and he could only be patient. “The frustrating part was there was no one to call who had this, no other thrower,” Manning says. “There was no protocol.”

Of all the traits Manning was born with, the one that served him best during those months wasn’t his analytical mind or his physical strength, but his painstaking temperament. Manning has always been the most exacting man who has played the position, compulsively meticulous, a turn-over-every-stoner. The quality helped him cope when he finally encountered a problem he couldn’t solve with arm strength.

“If you have a problem with Peyton’s intensity, take it up with the Lord,” Cutcliffe says.

Keeping the injury in perspective

In July 2011, with his arm still unresponsive, Manning went back home to New Orleans for a dose of perspective from the people who knew him best, his parents and brothers. He did a little throwing with his younger brother Eli, quarterback for the New York Giants. He and Eli had always played a lot of catch. “We throw the same, with pretty good RPMs going both ways,” he says. But by this time, Manning’s grip was so poor that he couldn’t catch his brother’s passes; the ball slipped right through his hands. When he tried to throw it, the ball fluttered weakly through the air. Eli told him frankly, “It looks like you can’t finish the throw and get anything on it.”

But it was Manning’s older brother Cooper who put his neck injury in the proper context and cured him of any self-pity. Cooper had been an athlete equal to anyone in the family, an all-state wide receiver with a scholarship to Ole Miss, when he began experiencing numbness and atrophy in his right bicep. The Mannings flew to the Mayo Clinic in Minnesota, where tests showed dangerous degeneration in his spine. He underwent surgery to relieve the pressure on his spinal cord, and complications set in. After weeks in a wheelchair, he had to walk with a cane. All of which Manning had witnessed up close, even as his own development was climaxing.

“I’ve never taken it for granted, ever since Cooper’s career was taken from him just like that,” Manning says. “So I always had it in perspective, and I didn’t need a year off to remind me how lucky I was to play.”

He and Cooper talked, comparing their conditions — but in truth, Manning realized, there was no comparison. He had gotten a career, and Cooper hadn’t. “Maybe this was my not-picture-perfect-neck catching up with me finally,” Manning says. “I just thought, wow, I got almost 20 years out of this neck. Boy, I’m grateful for the time I’ve had.”

Still, the meticulous part of Manning was unsatisfied. He sought second, and third medical opinions. He flew to Europe four times, trying various therapies or promised miracle cures, most of them having to do with electro-stimulation techniques to rekindle the nerves. “Some had a little voodoo to them,” he says. “When you’re injured and not recovering fast, it’s hard to dismiss those. You never knew if one might work, so I tried a few of those.”

He spent weeks in the weight room pumping embarrassingly low weights, five-pound dumbbells. He’d always been the kind of person who did 15 repetitions when 10 would suffice, but no amount of reps would make the nerve come back faster, and overwork was the worst thing he could do. Trying to throw was like “stepping on the gas and there is no gas in the car,” he says.

“Sometimes progress was not going backwards,” he adds. “It was just a real test of patience unlike anything I had to go through. There was nothing I could do about it.”

Not only was his arm weak; he had a weird sensation that he was no longer sure of where it was when he threw. At one point he tried to fire a ball and it flew a full 12 yards wide of the target. “It’s hard to explain but I kind of lost awareness of my arm in space,” he says. “When you had the same throwing motion for so long — golfers talk about repeating their swing, well, quarterbacks repeat too. But I couldn’t repeat. That was scary. Just discouraging.”

He fought to keep a good attitude, hoping that the arm would somehow dramatically improve at the last minute, so he could show up at the Colts’ training camp. For four months, he woke up every day and told himself that today was the day his arm would come back alive. “You talk about being pretty disappointed around two in the afternoon when you realize today is not the day,” he says.

That September, the disc re-herniated yet again. This time, Manning sought a permanent solution: a fusion to stabilize the neck. It would be his fourth surgery in two years. He sat down with Archie and Olivia, who were concerned that his priority be his health and not football. Manning explained that he was going to give it just one more try.

“I’m gonna work as hard as I can, and listen to the doctors,” he said. “And if the doctors say I can’t, then it’s been a good ride.”

Baby steps, small measurements

At the start of the 2011 season, Manning was in another hospital bed recovering from a single-level anterior fusion: a spinal specialist named Robert Watkins removed the damaged disc from his spinal cord, filled the space with a bone graft, and welded the vertebrae together with a plate and screws. This time when Manning woke up, he could barely throw a dart. The game was prescribed as part of his rehab, but the first time he tossed one, he couldn’t penetrate the dartboard. “I could barely get the thing to stick,” he says.

For almost three months he didn’t touch a football. His friend Cutcliffe advised him, “Stop throwing.” Forcing the issue wasn’t healthy, and could create other problems in his elbow or rotator cuff, Cutcliffe warned. Also, “It’s bad for you to see yourself throwing poorly. So stop throwing.”

When he did finally did pick up a football again, it was just to throw a few gentle lob passes to his wife, Ashley. There was a sweetness to their games of catch: In April 2011, the couple had welcomed twins, Marshall and Mosley. Caring for the newborns gave Manning a deep contentment even as he dealt with the prospect of retirement. “I had a real peace,” he says. “I don’t know if many people believe that, but I had a peace if this was not to be.”

Compared to being a father, a football comeback seemed like a vanity project. “I don’t want to be selfish,” he told Archie. Devotion to parenthood had been his father’s greatest talent, and Manning wanted the same for his family. “I’m not sure it would have been as easy if I wasn’t coming home and playing with them every night,” Manning says. “The one year the Lord took my greatest physical gift, he gave me the greatest gift you could have in children. So that was a real equalizer. And I would take that trade any day of the week.”

When Manning did begin to throw seriously again, he moved slowly and deliberately. For weeks he sat in front of a mirror and practiced his throwing motion, over and over, until it looked familiar again and he could repeat it. “So that was step one,” he says. “I said, ‘At least I know where my arm is.’ ”

Step two was a December 2011 trip to the Duke campus to begin work with Cutcliffe, who had watched him since he was 18 and understood him better as an athlete than anyone except his father. Cutcliffe designed a program of baby steps and small measurements, with the idea of rebuilding Manning’s confidence, along with his arm mechanics. “We started at ground zero,” Manning says. “It was good going to someone who knew you from the beginning.”

They worked in secret, because Manning continued to be highly self-conscious and by no means convinced he could make it back. Though he was not in pain and the disc problem had been solved, the surgeries had left his right arm significantly weaker than his left. Holding sessions around Cutcliffe’s collegiate schedule, sometimes in the pre-dawn or at 11 p.m., they began with the simple, fundamental task of regaining the feel in his hand. “You actually throw a ball with your fingers,” Cutcliffe says. Before Manning could throw an NFL-quality ball, they had to address whether he’d be able to even hold a snap firmly enough.

“The toughest part was the emotions of, you go from being as good as there is on earth, to relearning how to do it,” Cutcliffe says. “And that was interesting. It was an interesting challenge for a guy as good as he is in the world, to have to work on every single minuscule thing.”

They worked on his setup — the same movements he had practiced as a 3-year-old. Each day Cutcliffe filmed Manning’s release, and measured the velocity of his passes and his arm speed. The numbers steadily inched up — and then began to show dramatic progress.

Next, Cutcliffe addressed “his intention to release,” the subtle moment when a quarterback, looking downfield, makes a decision and begins his first movement to throw to a target. Great players in a secondary don’t just try to break on the ball; they try to break even earlier, on the “intention” of the quarterback. Manning worked on shortening the time between his decision and actual release. He got quicker and more accurate by the day.

“When he saw himself getting back to his normal, when he could get the ball into his arm slot, and felt it, God, that was fun to see,” Cutcliffe says.

“He just flat out got better”

In February 2012, Watkins declared Manning’s neck firmly fixed and fully healed, and cleared him for NFL play. He was no more at risk of injury than anyone else on the field. But Manning still had weakness in his triceps; the nerves hadn’t completely regenerated and the question of whether they ever would remained. Manning would simply have to work around it, Watkins told him. “It’s your job to learn to compensate for that,” Watkins said. The key would be to get his legs, core, and other arm sections as strong as possible.

“What he kind of said was, ‘I think you can still be a thrower with a weak triceps, but everything else needs to fire pretty good,’ ” Manning says.

But that prognosis wasn’t good enough for the Colts, who on March 6 released Manning and announced their intention to go young and draft Andrew Luck with the No. 1 pick. Now a free agent, Manning’s workouts gained an added intensity — and became a source of national theater when he announced he would conduct a series of private auditions for clubs of his choice. He and Cutcliffe went into intensive preparations for them. “It was a full-court press situation,” Manning says.

On the surface, Manning seemed in charge of the process, from his gracious farewell at a Colts news conference to his cherry-picking of teams he was interested in, settling on the San Francisco 49ers, Tennessee Titans and Broncos. In reality, Manning was anxious. On March 15 he had his first audition, in front of 49ers Coach Jim Harbaugh and offensive coordinator Greg Roman. He was as nervous as he had been as a collegian at Tennessee trying out for pro scouts. “Maybe even more so,” he says. “I haven’t felt like that in some time, because I really wasn’t sure of my physical state, I was still learning what I could and couldn’t do, and now someone who was not a friend was going to come and watch.”

Harbaugh and the rest of the NFL coaches wouldn’t sugarcoat anything, Manning knew, and he didn’t want them to. After months of secrecy and clandestine workouts, it was time to expose himself. He wanted the harsh truth, a final judgment on whether he could still play the game. He stripped down and underwent a full physical like a horse on an auction block, showing everything.

“I wanted them to see me in person,” he says. “All of them felt my muscles. You could see the atrophy in my arm and right pectoral. I wanted to put it all out on table, and have them say, ‘Here’s what we think,’ rather than show them a video of me. I wanted them to tell me, ‘Hey you look good enough to play for us.’ ”

By the end of March, the Broncos decided he was good enough and awarded him a five-year deal worth $96 million. But even then, Manning still had huge strides to make. In July 2012, he went back to New Orleans to join his family for their annual football camp, and he did some throwing with his father looking on. He was three weeks away from his first training camp with the Broncos. Archie thought he looked . . . just okay.

“Wasn’t bad, wasn’t ugly, but it wasn’t Peyton,” Archie says. “I thought he could play, but I didn’t know how his game was going to change. I knew what made him the quarterback he was, but he had a new team, a new system, and a new body he was playing with. So I had no idea he could be as productive as he was.”

Manning continued working on the program he had drawn up with Cutcliffe, and the long awaited dramatic jump in strength finally came. And then kept coming. As it turned out, his spectacular debut season with the Broncos, with 37 touchdown passes, was merely an appetizer. How could there be room for improvement? But there was. “This year at age 37, he got better,” Archie marvels. “He just flat got better.” He pauses. “We been at this a long time,” he says. “But yeah, we are very proud of him. Let’s keep it going. Just keep him healthy.”

Cutcliffe says that the Manning of this season is much stronger than last, and in some ways than he has ever been, given his new emphasis on legs and core. And he still may not have found his best form. “It’s going to do nothing but get better as he continues to regain strength,” Cutcliffe says. Add to his physical improvement the fact that the Broncos have surrounded him with more weapons and the best supporting cast he has ever had.

Cutcliffe believes the injury forced Manning to be more exacting in his habits than ever, and that the Broncos’ explosive numbers this season reflect the fact that he has exported those habits to his teammates. He developed an almost intuitive relationship with his primary receivers, Wes Welker, Demaryius Thomas and Eric Decker, after a summer of “hard, hot work” with Cutcliffe at Duke. “The entire mentality is catching on and it makes everybody play better,” Cutcliffe observes.

Nevertheless, it is scarcely believable that the NFL passing leader is a 37-year-old with metal in his neck. Here is an even more incredible fact: To this day, Manning’s right arm remains slightly weaker than his left. He still works on that right triceps and nerve, but is resigned to the possibility that they might not ever come fully awake. “I couldn’t tell you whether they’ll come back, and until I stop playing I won’t stop trying,” he says.

He makes up for it, he says, with other things. Like timing, recognition, and disguise. He got some advice from Bill Parcells, the two-time Super Bowl-winning coach who is now an analyst for ESPN: Parcells, a big baseball fan, told Manning not to worry so much about throwing strikes, but to think more like a pitcher and throw junk. “Can you still get ’em out?” Parcells asked. Manning replied puzzled, “What do you mean?” Parcells answered, “There are different ways to move the chains. Can you get it in the end zone is what matters.”

So these days he thinks less about throwing missiles or glamorous arcs, than about just tricking the opposition and delivering the ball to the right place. The golden boyness has faded; in its place is a man with a fighter’s face, narrow eyes and a slightly hooked nose that keeps him from being pretty, hair mowed short as a putting green, and expression closed shut, refusing to give anything away to the opponent. Defensive backs describe trying to read Manning’s face as he scans the field, nothing moving under center except his predatory eyes, “flicking back and forth,” as Eagles safety Earl Wolff says.

He has become an expert in replacing natural gifts with compensatory skills. He’s learned he doesn’t need the old velocity, that he can drive the ball strongly enough with his legs, and win as much with good decisions as great throws. “Maybe certain throws you don’t make anymore,” Manning says. “Or you throw a little sooner. You learn to adjust your mind, have maybe even more of a sense of timing.”

The result is that he now views his career as a sort of split image, before and after. There is the Before Manning and the After Manning — and this one plays entirely in a grateful present.

“I really don’t compare myself anymore to how I was before,” he says. “I’ve learned to throw in this state, and I’m just trying to do the best I can with the way things are.”

Which may end up being better than anyone has ever done it.