Almost perfect is never enough for Bill Callahan. The Washington Redskins’ interim head coach lives in details that are too small for anyone else to see and too obscure for anyone else to appreciate. To Callahan, a play is more than just X’s and O’s with arrows jutting across a page; it’s an idea that can result in an infinite number of potential outcomes, each of which must be imagined and assessed while accounting for external factors such as wind and rain and the slipperiness of the playing surface.

And even then he might not be satisfied.

“Science,” a former colleague called Callahan’s approach to offense.

“Obsessive is the right word,” said Callahan’s son Brian, the Cincinnati Bengals’ offensive coordinator.

Perhaps the biggest criticism of former Redskins coach Jay Gruden is that he didn’t focus enough on detail. If that assessment is valid, then the team just transitioned to Gruden’s polar opposite in Callahan, a man so lost in minutiae that he bewilders players and assistants.

Callahan, 63, will serve as a head coach for the first time in 12 years Sunday, when the 0-5 Redskins, lost in organizational chaos, play at the 0-4 Miami Dolphins. It would seem to be the worst scenario for a man who happily had been coaching offensive linemen for the past decade, but Callahan has seen mayhem before. He coached Al Davis’s Oakland Raiders for two seasons, taking them to the Super Bowl in his first year, and then led Nebraska through four uncomfortable seasons. His friends say he never changed as turbulence whirled around him. He did what he has done for decades as an offensive line coach: He kept pushing, demanding, trying to make every detail perfect, every possibility studied.

Sometimes it can be confounding to be around Callahan. Upon being hired as Callahan’s assistant offensive line coach last year, Phil Rauscher was handed the following assignment: Break down every running play that happened in the NFL during the 2017 season. It took Rauscher a week. Callahan wanted it sooner.

“Then we watched them and studied them,” Rauscher said. “And then we watched them again. I think we watched them two or three times. We still go back and watch them.”

That’s Bill Callahan. His brain is almost like an old-fashioned library card catalogue with its own Dewey Decimal system, allowing him to instantly pull up practice drills from years before, remembering everything from a day everyone else has forgotten.

“There’s a clip from practice on Sept. 23, 2010; Phil, can you pull that up for me?” Redskins offensive lineman Tony Bergstrom said, imitating his position coach of the past few years.

Rauscher can’t remember how many times he has spent hours intricately drawing a play on a computer, making sure to get every detail just right, only to have Callahan hand it back to him because the angle of one line is off by the tiniest little bit. Often the imperfection is so small that Rauscher can’t even find it without magnifying the image “10,000 percent,” and even then it’s hard to see what is wrong.

And then there are the notebooks.

For 40 years, since Callahan got out of Benedictine University, he has been chronicling his football life in graph-paper notebooks, etching plays and jotting thoughts and ideas in immaculate, freestyle handwriting so tiny that two lines of his script would fill a single line of a standard legal pad.

The notebooks piled on office shelves and desks and eventually in his garage. Brian and his sister and two brothers have made periodic attempts at organizing them. Once, they bought several storage cabinets to keep the notebooks from spilling across the garage floor. This summer, he tossed several of them in the trash.

Throwing away decades of observations from what Brian called “a beautiful mind” seems wasteful. But four decades make for a lot of notebooks the way Callahan fills them.

“He’s kept the important ones,” said Brian, who paused before adding: “He’s also become more adept with his computer usage.”

Focus amid chaos

Callahan practices are tough, in part because he’s tough — the son of a policeman from Chicago’s South Side — but also because nothing is ever perfect. Since he came to the Redskins in 2015, the team has had what amount to two practices: the regular team practice and Callahan’s offensive line practice. When the regular practice ends and the players go inside, Callahan’s linemen remain on the field no matter how hot or cold it is or how hard the rain is falling.

You would think his players would hate this. They don’t. Though a few have complained quietly that his long practices might have contributed to the injuries that have plagued Washington’s offensive line in recent years, most say they love that he spends so much time pushing them, demanding they be better. Ereck Flowers, who had failed as a left tackle with the New York Giants, chose the Redskins in free agency specifically because of Callahan, who has turned him into a solid starting guard.

But there is another part of Callahan’s story, more complicated but pertinent to his current position: the six years he was head coach of the Oakland Raiders and Nebraska Cornhuskers and the awkward way both jobs ended.

Callahan’s quarterback in Oakland, Rich Gannon, won the MVP running the new pass-first offense Callahan installed after replacing friend Jon Gruden in 2002. Gannon said the six years he played with the Raiders “were the hardest of my career.” As owner, Davis was endlessly demanding, controlling which players came and which left, forever hiring and firing new coaches.

“Bill did an amazing job despite the circumstances,” said Gannon, now an NFL analyst for CBS. “It wasn’t an easy work environment. The atmosphere was dreadful in the building.”

Callahan, though, designed magnificent game plans, spending six hours on the day before a game with his offensive coordinator, Marc Trestman, trying to come up with the perfect first 15 plays, parsing each for every potential calamity. They went to the Super Bowl that first year, losing to Jon Gruden’s Tampa Bay Buccaneers. But the second season, the Raiders succumbed to chaos once again. There were injuries. Stars were unhappy. Wide receivers Jerry Rice and Tim Brown accused Callahan of sabotaging the Super Bowl by changing the game plan the day before the game. After going 4-12 in 2003, he was fired.

Nebraska hired him just days later, but the fit was awkward from the beginning. Program supporters were trying to cling to the glory years of famed coach Tom Osborne, and many fans didn’t see the need to change the old Nebraska power running attack to a more modern West Coast offense. Callahan being Callahan, he plunged ahead, scribbling in notebooks, pushing for perfection.

The Cornhuskers were 5-6 his first season, and though they went 8-4 and 9-5 the next two years, Nebraska fans wanted more. There didn’t seem a full connection between coach and fans or coach and players. Several players complained about communication.

Former Redskins defensive end Adam Carriker, who played for Callahan at Nebraska and personally liked him, nonetheless sensed the coach seemed “upset” about his firing in Oakland and came straight to Nebraska trying “to change everything” about the program.

“I honestly believe he had a lack of respect for what we had here at Nebraska,” Carriker said. “I don’t think he had a full understanding of what was here, and I don’t think he wanted to.”

Still, Callahan recruited well, bringing in players such as future NFL star Ndamukong Suh, “connecting” with high school players and their parents, recalled his defensive coordinator, Kevin Cosgrove. But after the Cornhuskers crashed in 2007, going 5-7, Callahan’s time in Lincoln was over.

He retreated to the anonymity of coaching offensive linemen in the NFL, first with the Jets and then the Cowboys before coming to the Redskins when Jay Gruden was hired.

“I think he really enjoys coaching offensive linemen,” Brian Callahan said. “I’m sure if someone had said, ‘We want you to be a head coach again,’ he would have said, ‘I’ll do it.’ But I think he was content coaching offensive linemen as long as he wanted to coach.”

And searching for the details that no one else sees.

Getting it right

Want to understand Callahan’s impact on a play? Take the lone Redskins offensive play anyone remembers from Sunday’s loss to the New England Patriots: Wide receiver Steven Sims Jr. cut across the backfield, took a handoff from quarterback Colt McCoy, cut right, dodged two tacklers and ran 65 yards for Washington’s only score.

Redskins coaches had seen Georgia Tech run the play and decided early in the week to run it against the Patriots. Callahan spent parts of two days researching the possible pitfalls. But when the team ran it in the Friday morning walk-through, Callahan was bothered by something.

After practice, Callahan watched video of the walk-through, examining the way each player moved and how his hands followed the block. Ultimately he decided they had to change the way they held their hands. A seemingly insignificant detail, Rauscher thought, as Callahan explained it to him. But Callahan was determined.

“Lo and behold when the play got snapped, that’s what helped break it open,” Rauscher said before pausing. “Sometimes I’d like to think a normal guy wouldn’t have thought to change that.”

Normal, though, isn’t piles of notebooks and unrelenting demands for perfection.

“Bill’s a different guy,” one Redskins official said recently. “He isn’t really social.”

Callahan rarely does interviews, and old friends who sent him congratulatory texts this week said he deflected the attention back to them, refusing to make the moment about himself. In a rare moment of reflection at a recent news conference, he said, “I’ve taken inventory of myself and really tried to improve myself in respect to try and be a better coach for the player.”

When pressed to say how he has changed, he said, “I think I’m more patient.”

Then he started to talk about the science of coaching offensive linemen, about the way each player has to move and how complicated a process it is to get each piece moving just right.

“There’s so many details,” he said.

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