Over the last decade, the most riveting rivalry in the NFL may have come not from two teams, but rather two individual players. The head-to-head matchup of Peyton Manning vs. Tom Brady is always one of the most anticipated games of the NFL regular season, and the star quarterbacks meet again in Week 9.

Sunday’s game takes on the usual significance of a regular-season matchup between the two players. Whether Manning has been on the Indianapolis Colts or the Denver Broncos, he and Brady are often leading two of the best teams in the AFC. Their eight combined Super Bowl appearances and seven MVP trophies make them the top quarterbacks of their generation, putting them in the discussion for greatest of all time.

This time around, though, extenuating circumstances could make Sunday’s contest more special than most. With Manning approaching his 39th birthday and Brady just a year younger, the New England Patriots quarterback realizes his encounters with his counterpart could soon be coming to an end.

"Five, six years ago you don't think about those things," Brady told WEEI-93.7 FM in Boston. "But as you mature a little bit and realize this could always be the last one, then you do. It's pretty special.”

Following the Patriots’ slow start to the season, ESPN reported that tension with the coaching staff could mean that Brady’s time in New England might not be far from ending. That appears unlikely, however, considering Brady and the Patriots, once again, look like Super Bowl contenders.

The debate surrounding Manning vs. Brady is constant, but there has been more talk of their legacies this season than ever before. Since the start of last year, Manning has put up historic numbers, throwing for 77 touchdowns and just 13 interceptions, as well as setting the record for career touchdown passes. Brady looked like he might be fading into the twilight of his career, but 14 scores and no picks in the last four games have silenced his critics.

Last season, the quarterbacks faced off twice, with New England winning the regular-season matchup and Denver coming out on top in the AFC Championship. Brady has gotten the better of Manning in 10 of their 15 meetings, but the Broncos quarterback has won two of their three playoff matchups.

Despite the unbelievable run that Manning finds himself in, he could have trouble on Sunday. New England head coach Bill Belichick has found a way to contain the best regular-season quarterback of all time, limiting him to 31 touchdown passes and 20 interceptions. Manning’s 1.55 touchdown-to-interception ratio against the Patriots is worse than the 2.31 ratio he’s enjoyed throughout his career.

While Belichick has had his share of success against Manning, he’s still able to appreciate the quarterback's greatness.

"I mean, [Manning is] great, he's obviously a great quarterback," Belichick told reporters. "The best quarterback I've coached against."

Brady has been much more efficient than Manning when facing his rival, tossing 27 scores and 12 interceptions. A large portion of those numbers were compiled against the Colts, who weren’t known for having a stout defense when Manning was at the helm.

In Week 9, Brady will face, perhaps, the best defense that has been part of a team quarterbacked by Manning. Denver ranks fourth in the NFL in total defense, and sixth in opponents passer rating.

Even if Manning and Brady weren’t playing in the Week 9 contest, it would still be the most important game on the schedule. Denver’s 6-1 mark is the best record in the AFC, and a victory would give them a firm grasp of the No.1 seed. A victory for New England would give them sole possession of the top spot in the conference.