Manning set a record when he tossed his fourth touchdown pass of the game Sunday against the Houston Texans -- and 51st this season -- on a scoring strike to tight end Julius Thomas in a blowout victory, which clinched the AFC West title for the Broncos.
"It's an incredible feat," Brady said in a radio interview with the "Dennis & Callahan show" on WEEI sports radio in Boston. "To throw 50 like we did in 2007 was incredible. [Dan] Marino threw 48, then Peyton threw 49, and I was lucky enough to be on the team to throw 50.
"And 51 is unbelievable through 15 games, they've been throwing at an incredible pace, and what they've done offensively and certainly in the passing game has been incredible."
Passing numbers have soared around the league in recent years, with Manning on pace to also break Drew Brees' record for passing yards in a season with a strong Week 17. Nonetheless, Brady said that throwing touchdown passes has never been an easy task in the NFL.
"It's hard to throw one in a game, and to throw four, five or six, like what he's done over this year," he said. "I remember in 2007 we were throwing them, and I was like, 'Oh my god.' You play all these years where you have not a lot of touchdown passes, and all of a sudden you're throwing four a game. It's pretty incredible."
While Manning's 51 (and counting) stands as the record for now, Brady is confident the number will be passed someday.
"I'm sure at some point all of these records are going to be broken; that's just the way records are," he said, before adding, "but it's a pretty remarkable achievement."
Manning said Sunday he also believes his record will fall someday.
"I think it's a unique thing and a neat thing to be a part of NFL history, even though it may be temporary," he said. "So I'm going to enjoy it as long as it lasts, and hopefully the Hall of Fame will send the ball back once somebody throws for more."
This season won't rank among Brady's most productive in terms of touchdown passes and yards, but a strong stretch of play has helped keep New England in contention for the top seed in the AFC.
The Patriots (11-4) can secure a top-two seed and a first-round playoff bye with a win Sunday against the Buffalo Bills (6-9). They would earn the AFC's top seed with a win and a Broncos road loss to the Oakland Raiders (4-11).
Brady is on pace for his lowest touchdown total since 2006 (excluding 2008, when he played just one quarter before suffering a torn ACL), but he isn't focused on personal achievements with the regular season winding down and the playoffs on the horizon.
"I think you want to play as best you can -- that's the only thing that matters," he said of records. "However, you need to contribute to help the team win games, that's really what it's always been about for me.
"I think the individual awards and accolades, to me they don't, they're not, they just don't weigh as much on my mind as doing what we're ultimately trying to do, which is win it all. That's always the most important thing for me in a team sport."