DENVER (AP) Not since he was a skinny 18-year-old freshman at the University of Tennessee has Peyton Manning served as a backup.
With his longtime understudy Brock Osweiler making his seventh straight start for Denver on Sunday, Manning will be the No. 2 quarterback for the first time since replacing an injured Todd Helton against Mississippi State on Sept. 24, 1994.
That's 7,772 days.
A fourth interception in a loss to Kansas City in mid-November, and a searing jolt of pain in his left foot, brought a premature end to Manning's day and maybe even his magnificent career.
Manning, who remains tied with Brett Favre for most regular season wins - 186 - by a starting quarterback, spent the next six weeks in street clothes before being able to suit up again.
His legacy, though, was on display in every single NFL game played during his absence.
Like Lawrence Taylor and Reggie White on defense or Jerry Rice and Don Hutson at wide receiver, Manning changed the game itself.
''He was on the forefront of basically a revolution in the way offenses are run in the National Football League,'' Joe Theismann said. ''His footprint was bigger than just the cities he played in. He transformed the position. The style of offense that he ran in Indianapolis was revolutionary and nobody ever figured out how to stop it there - or in Denver.
''The only thing that's basically slowed Peyton Manning down was Father Time.''
Whether or not he's back in the shotgun this month or next season hollering out ''Omaha!'' No. 18 has left an indelible imprint on America's most popular sport. And on Madison Avenue.
His dry wit and star power have been a staple of late-night television and 30-second commercials for nearly two decades. And when he stepped onto the football field as the top overall draft pick by the Colts in 1998, Archie Manning's kid was equal parts transcendent and throwback.
A pioneer in the way he deciphered defenses and directed play at the line of scrimmage, pacing from tackle to tackle, pointing and hollering, he became a model for every quarterback who's come along since. He was at the vanguard of the aerial fireworks shows that light up today's scoreboards and big screen TVs.
''I think from the sense of quarterbacks, he's been fast-paced, no-huddle, dynamic offense, score a lot of points, and score quickly,'' said his brother, Eli Manning, a two-time Super Bowl winner for the Giants. ''He has won a lot of football games. Now you see that more. More teams are doing it. The Colts kind of started that trend and did it well for a long time.''
So did the Broncos, where Manning threw 140 of his NFL-high 539 TD passes, including a record 55 in 2013.
Manning was also old-school in the way he served as his own de facto play caller, endearing him to the players of a previous epoch, noted former All-Pro safety John Lynch, whose playing career spanned Manning's arrival.
Lynch called the five-time MVP a ''genuine game changer'' and said he's among the biggest reasons the NFL is so popular.
''I started in `93, my preseason went like this: Marino, Elway, Kelly and then we opened against the Chiefs and Joe Montana. So, I caught that era, and now I caught this current era,'' said Lynch. ''And so much of your opinion of who's the best ever is how you fared against them, and my teams never fared well against Peyton Manning. He was always one step ahead of us.''
Manning was never the best athlete, but his off-the-charts preparation and other worldly memory recall made him rise above the rest, suggested DeMarcus Ware.
''He beat you mentally,'' said Ware, who came to Denver for the chance to play with Manning after the Cowboys released him. ''That was his guide: physically you might be faster than me, you might be more athletic than me, but I'm going to outsmart you every time.''
Manning's work ethic and machinations at the line allowed him to find the underbelly of any defensive formation, adjust accordingly, and deliver the pass with precision.
Broncos guard Evan Mathis also came to Denver to play with Manning, and he said the passer's perfectionist style was infectious.
''You have your natural leaders, and he is in that category. You're not only learning schematics or on-the-field stuff, but you're learning and seeing proper habits,'' Mathis said. ''That kind of stuff is contagious.''
Theismann said Manning's ''understanding of the game and work ethic were at the highest standard. He was the barometer by which so many measured excellence in the league. Brock's had literally the best seat in the house to be able to learn.''
Indeed, Osweiler said, ''There's not a day that's gone by since I've been in the league that I haven't learned something from Peyton.''
Broncos receiver Demaryius Thomas said he, too, has been blessed to work with Manning because ''when you see him on the field, you want to be perfect, too. And before long, you're better than you thought you could be.''
Former Colts cornerback Marlin Jackson, whose interception of Tom Brady helped send Indianapolis to the Super Bowl the year Manning won his only championship ring, said: ''That's what the game is like playing with Peyton Manning, taking it to another level about how you view yourself and your career to want to be great.''
Manning missed all of the 2011 season following neck fusion surgery. This year has been agonizing, too.
Bothered by a torn left plantar fascia for months, Manning threw just nine TD passes and 17 interceptions - which still leads the league even though he hasn't played since Nov. 15.
While he was sidelined, several unsubstantiated reports painted the league's only five-time MVP as a bad teammate or a cheat. The NFL Network alleged he'd refuse to serve as Osweiler's backup once healthy, and Al Jazeera reported Manning obtained HGH from an anti-aging clinic in Indianapolis, although his accuser recanted.
Those reports pained teammates and friends.
''It does, incredibly,'' said Lynch. ''Because the guy's had such a wonderful career. He's meant so much to this league. Those are the things that really bother me, because he frankly doesn't deserve it.
''He's never been a backup in his life. This is all new to him. But his attitude is incredible. I mean, he said, `Hey, I'm trying to get healthy, I'm doing everything I can to be the best support to Brock.' And any notion that he's told them, `Hey I'm not going to be your backup,' that's garbage,'' Lynch said.
Lynch tells a story about he and Manning were driving to Colorado Springs on a golf outing when they saw a group of kids playing football at the park. Manning looked over at Lynch and said, ''Let's surprise these guys.'' They pulled over and played with them for an hour.
''I've seen so much of that kind of stuff, it's a shame all this other stuff comes up,'' Lynch said. ''He's a big boy. He'll handle it well, and he has. But you feel like this is a guy who should have the opportunity to go out on top.''
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AP Sports Writers Michael Marot and Tom Canavan contributed.
Follow AP Pro Football Writer Arnie Melendrez Stapleton on Twitter: http://twitter.com/arniestapleton