But there are at least a dozen men who have done it, and most of them say they wouldn't want to snap to anyone else. Here are some of their stories and memories of playing in front of two of the most iconic athletes in professional sports:
DAN KOPPEN, New England Patriots center, 2003-11, Broncos center, 2012-present
About an hour before Sunday's kickoff between the Broncos and the San Diego Chargers, Koppen was standing outside the locker room in street clothes, talking on his cell phone. Koppen tore his ACL during training camp, and for the past six months, he's been part of something big, but also feels as if he's watching it through a plate-glass window. Manning broke the single-season passing yardage and touchdown records in the NFL; the line gave up a league-low 20 sacks. And Koppen, who's used to being in the middle of the action, was on the outside.
As the Broncos celebrated their playoff victory Sunday night, Koppen, wearing a red hoodie, quietly slipped out into the windy night. He said he's happy for the guys. But this next week no doubt is killing him. The Broncos are playing New England -- his former team -- for a trip to the Super Bowl.
It didn't seem that long ago that Koppen was young and in control. His rookie year with the Patriots, Koppen got his first start in Week 2 at Philadelphia, when Damien Woody was injured. Things seemed to flow naturally between Koppen and Brady from the start. They went to three Super Bowls together, and Koppen has two rings.
He considers himself lucky, not burdened, to have played with both Brady, 36, and Manning, 37. They've got the tough jobs, Koppen says. He considered his easy in comparison.
"We had a good time," Koppen said. "I think Tom's more of that laid-back type. And Peyton has more of that coach attitude. He's really always grinding. And both approaches work for each guy. To each his own."
One of Koppen's favorite memories involves Brady and a photo shoot the quarterback did for GQ magazine in 2005. Brady was holding a goat in one of the poses, and the linemen had a field day with it. One practice, Koppen and Matt Light made copies of the goat photo and affixed them to the backs of their jerseys.
"If they ask you [to do it]," Koppen laughed of one of Brady's only ill-fated decisions, "you don't have to say yes."
Brady is one of his closest friends. There were never any long, detailed discussions with Brady about what he expected of him. Like every other Patriot, Koppen knew what was expected of him: Do your job, and do it to the best of your ability. "That came from the head coach," Koppen said.
He broke his ankle in a Week 1 game against Miami in 2011, was put on injured reserve and was one of the final cuts the next summer. When he was picked up by Denver, it seemed like a perfect fit. The offense was similar aside from some line calls and terminology.
Koppen didn't watch a lot of film with Manning, who was coming off neck surgery and learning a new system. They'd talk quite a bit to make sure they were on the same page. But as with Brady, Koppen always knew what he was getting with Manning.
"They want guys out there who know what's going on so they don't have to worry about another thing," Koppen said. "They want to know that the line is taken care of and that the fat guys up front are all set and they don't have to worry about that."