Tom Coughlin saw the signs six years ago, when his New York Giants players tuned him out because of a fundamental disagreement. They recoiled at Coughlin’s emphasis on details, which seemed like minutiae to many of them but essential to their coach.

He heard the whispers a year later, when new General Manager Jerry Reese and Giants ownership wondered aloud whether the team could win with Coughlin as coach, and might its chances be better with someone else?

And he was aware of renewed grousing last season, after a Super Bowl championship four seasons earlier had been buried under a 3-5 record to end the 2011 regular season — before a spectacular postseason run ended with Coughlin lifting another Super Bowl trophy.

“We call it midstream adjust,” Coughlin, 66, said last week, four days before another challenge, when the Washington Redskins and Robert Griffin III visit MetLife Stadium. “You’ve got to be able to do that in this business.”

In perhaps the most tenuous job in sports, when three seasons or fewer can determine the arc and narrative of a qualified man’s career, Coughlin has kept standing. Other NFL coaches come and go, try and fail, disappearing into the shadows. Some football men refuse to change, leaning only on what they know, even at the risk of their futures.

Coughlin, known earlier in his career as “Colonel Coughlin” because of his unyielding attention to the small things and his view of players as chess pieces, has survived by adapting — and his willingness to dramatically alter his personality and viewpoint.

“From his early years, he’s definitely lightened up a bit,” Giants quarterback Eli Manning said.

Coughlin has gone from a coach on the brink of repeated firings to a near certain future Hall of Famer. As he stood under an overhang at the Giants’ practice facility on a breezy Wednesday last week, players filed off the field and walked past their coach without worry that their smiles or conversations might lead to a scolding.

Coughlin said that change wasn’t easy. But in his case, it was necessary.

“When you’re somebody like me,” he said, “you’ve got to learn it the hard way.”

Afraid to have fun

They were preparing for another showdown, this one for a chance to play in the AFC championship game in the 1996 season. Some of the Jacksonville Jaguars’ assistant coaches spent the slow hours before they met the Denver Broncos in a second-round playoff game, by channeling their excitement into a few light moments. Randy Edsall, at the time the Jacksonville Jaguars’ defensive backs coach, put on a headset and, seeing the famous ring announcer Michael Buffer on the sideline, bellowed into the microphone, “Let’s get ready to rumble!”

Then a familiar voice responded. Edsall had no idea that Coughlin had been listening.

“That’s enough!” Coughlin, then the Jaguars’ head coach, snapped.

Edsall, now Maryland’s head coach, should’ve known the colonel might have been wearing a headset, too. Edsall had played quarterback at Syracuse when Coughlin was an assistant coach and heard often about improper footwork and extreme focus. He later worked alongside Coughlin in his early years as a coach. Coughlin was always watching, always paying attention.

“He wanted to win so bad, and he was always just wound so tight,” Edsall says now.

The Jaguars defeated the Broncos but lost to the New England Patriots in the AFC title game, and six years later, Coughlin was fired. The Giants hired him in 2004, and his way was immediately unpopular.

Players were fined not just if they were late to practices and meetings, but if they weren’t at least five minutes early. Rules were enforced but not always explained.

“There’s a reason for everything that you do,” Coughlin said last week.

The coach spoke to players without emotion, without smiles, without joy.

“At that time, it was like everyone was kind of afraid to have fun,” said Giants guard Chris Snee, who is Coughlin’s son-in-law.

The Giants went 2-6 to finish the 2006 season, and rumors surfaced that players had quit on their coach. In early ’07, after general manager Ernie Accorsi retired, new GM Jerry Reese met with team owners and discussed whether a change was necessary.

“The question was: ‘Where are we?’ ” Reese recalled recently.

Soon, Reese summoned Coughlin into his office. Yes, as the two men discussed, a change was needed.

Getting through to the coach

Reese and Coughlin talked that first day for a long time. Reese said they formed a bond immediately, and he asked the coach if certain things were really necessary for success.

“At the end of the day,” Reese remembered asking, “this rule — does it really matter one way or the other with the players?”

Coughlin would be keeping his job — Reese said that, despite the sour end in ’06, he saw signs of progress — but his new boss wasn’t the only one proposing a less stern approach. The team’s player-development director, former NFL and Virginia player Charles Way, had seen Coughlin interact with his 11 grandchildren. He wasn’t a snarling drill sergeant with them; why couldn’t he show players a glimpse of that? Somehow, this got through.

“That made sense to me,” Coughlin said.

Others suggested that Coughlin’s wife, Judy, persuaded him to find joy in his job and form bonds with the men who played and coached for him. He formed a players’ council to improve communication between the staff and the locker room. He asked players about their children, their backgrounds, their lives. He even sometimes made jokes.

“He’s somebody that you can talk to, and he’ll make you laugh,” Giants guard Kevin Boothe said. “People don’t realize how good of a sense of humor he has.”

That doesn’t mean he abandoned his attention to detail.

“The core of that man is still the same,” Snee said. “But he has just opened up.”

Coughlin’s team won 10 games during the ’07 regular season, but with a guaranteed playoff spot, the coach refused to rest his starters in a mostly meaningless final-week contest against the unbeaten New England Patriots. It made little sense; maybe the unrelenting colonel was back.

The Giants lost that game, 38-35, but Coughlin noticed a few weaknesses in the Patriots. When the Giants charged through the playoffs for a rematch with New England in the Super Bowl, players remembered that they had hung with the Patriots the first time. Who was to say they couldn’t win?

Coughlin’s decision had been controversial, but it paid off; the Giants won, 17-14, for the franchise’s first championship since the 1990 season.

Snee said it likely would not have happened if his coach and father-in-law hadn’t made a deal with himself: Change a few things, but without sacrificing his principles. Nor would the Giants have captured last season’s Super Bowl, after Coughlin again shook off rumors about his job security, Snee said.

Thinking about it, Coughlin smiled.

“I think I’m a better communicator,” he said. “I know I have more patience. I know I, on occasion, have some fun with these guys, which I might not have ever done.”

Another challenge

A phone rang a few hundred yards away, and the voice of Coughlin’s newest challenge came through.

“My job is to be a quarterback,” the young man said, “and when I am called upon to do other things that aren’t like most quarterbacks in the league, then I use that ability.”

Griffin represents an evolving NFL, the rebirth of the Giants-Redskins rivalry, and a new chance for Coughlin to prove that, even as the league’s oldest coach, change is no threat to his team or his legacy. If that’s not enough, Sunday’s game will be for first place in the NFC East.

“I would never bet against Tom Coughlin in a big spot,” Reese, the Giants GM, said.

Rather, Reese and the Giants bet on a long shot and won bigger than most anyone could have imagined. Standing in the shadow of that overhang with his hands in the pockets of a windbreaker, Coughlin eased toward the door. Meetings and preparations and details lay ahead, the same as ever.

Before he walked inside, he smiled as he talked about winning those two Super Bowls.

“As bad as it sometimes had been,” he says, trailing off. “. . . I think perseverance and persistence and never losing sight of the goal and surrounding yourself with guys who believe in the same thing you believe in — I think that’s what it is.”

He continued, pondering a word used to describe him.

“Survivor? You know, there’s a lot more good days than there are bad days. I’ve been able to recognize that.”