DENVER -- Only one of them can be the greatest.
Peyton Manning could be the one -- owner of a record four, working on five, Most Valuable Player awards, current holder of NFL single-season records for passing yardage and touchdowns and architect of a career-reviving second act, the likes of which has rarely been seen in any sport.
Tom Brady could also be that man -- leader of five Super Bowl teams and winner of three titles, one-time holder of some of the records Manning holds now and author of an undefeated regular season. He also has that 10-4 record against Manning despite constant turnover on his roster and a lack of a star-studded receiving corps.
Manning and Brady will meet Sunday for the 15th time, and the fourth time in the postseason, when the Broncos (14-3) face the Patriots (13-4) in the AFC title game.
The winner between the top two quarterbacks over an era in which quarterbacks have never been so good will get what could be the last say in the debate over who goes down as the greatest -- not so much because of what the win-loss numbers will say but because this could be the last time they meet with the stakes so high.
"I don't know that there will ever be another rivalry like it, or has been a rivalry like it," said John Elway, whose own rivalry with Dan Marino was held to only three meetings because of scheduling quirks over their decade-plus careers.
The game will either give Brady a chance to match Joe Montana and Terry Bradshaw for a fourth title or afford Manning the opportunity to win a second ring, which would put him one behind Brady, and in the same company with his brother, Eli, Roger Staubach and Elway, among others. It would also make Manning the first QB to win championships with two different teams.
While paying ultimate respect to each other -- "I feel like he's been a better player each year than he was the year before," Manning said -- neither quarterback professes to care much about how their own head-to-head showdowns will define their legacy.
Don't believe it, says Phil Simms, who admits in retirement that the smile was a little wider after he walked off the field with a win over a Staubach or Joe Theismann.
"It's always personal, no matter what," Simms said. "It's part of being a competitor and doing what you do."
One reason Brady has a .714 win percentage in the head-to-head meetings and also holds a 2-1 advantage in the playoffs is because, more often than not, he's been surrounded by the more complete team.
He has been anything but a one-man show in New England this season, illustrated best by the fact that the Patriots are in the AFC title game even though Brady threw for 25 touchdowns -- less than half of Manning's record-setting 55.
Without Rob Gronkowski, Aaron Hernandez or Wes Welker to throw to, Brady made it work, with a big assist from head coach Bill Belichick and offensive coordinator Josh McDaniels, who used to coach the Broncos.
New England's running game, led by LeGarrette Blount and Shane Vereen, has averaged 214 yards the last three games. Brady's 75 passes over the last three games are the fewest of any three-game stretch in his career.
Welker, who played with Brady for six years before coming to Denver this season, says it's not so much stats or physical attributes that defines these two Hall-of-Fame quarterbacks.
"They do a great job of keeping guys accountable, and their leadership skills and everything else," he said. "They are two guys you want quarterbacking your team. It's a toss-up between those two."
Manning has thrown for 92 touchdowns since arriving in Denver at the start of the 2012 season, his neck rebuilt from multiple surgeries, his future uncertain because of his weakened throwing arm.
He'd be the first to admit he's not the same as he once was, physically. But nobody prepares better.
His record-setting 5,477 yards and all those touchdown throws came with a gifted group of offensive stars surrounding him -- Welker, Eric Decker, Demaryius Thomas and this season's difference maker, 6-foot-5 tight end Julius Thomas. But Manning had great players around him in Indianapolis, as well, and never put up these sort of numbers.
"Honestly, no one will probably ever break that, not in this day and age," former Broncos receiver Rod Smith said.
On Sunday, Brady, who missed parts of practice early in the week with the flu, will be going against a depleted secondary that just lost cornerback Chris Harris Jr., which will make Champ Bailey -- injured most of the season -- a bigger cog for the Denver `D.'
And the Patriots will likely invite the Broncos to run-- much the way they did in their 34-31 overtime loss in Week 12 -- knowing the best chance of beating them is by taking the ball out of Manning's hands.
This 60 minutes (or more), their first title-game meeting since Manning's 38-34 comeback win en route to his first Super Bowl in 2007, could mark the last time the top two QBs of their -- or any -- era meet for these stakes.
Brady is 36 and, though relatively healthy, he has taken a beating over his career. Some say the Patriots, their roster decimated by injuries, defections and the arrest of Hernandez, got this far on smoke and mirrors this season. How much longer can they hold things together at a championship level?
And Manning? He is 37 and his future will largely depend on how his neck looks when doctors examine it during the offseason. The Broncos, meanwhile, are built to win right now, and have made it this far despite a rash of injuries on both sides of the ball.
No guarantees about the future.
"They're thinking about it during the week," Simms said. "When they play, they play. But when it's over, one of them will go, 'Yep, I got him again."'