Elias Sports Bureau, the league's official statistician, reviewed a 7-yard pass from Manning to wide receiver Eric Decker and determined it will remain a forward pass and not a lateral, which would have made it a 7-yard run.
That would have subtracted 7 yards from Manning's total, leaving him with 5,470 yards, six shy of Drew Brees' 2011 record.
"The stats crew at the game scored this play as a forward pass. During the course of a season, there are many similar plays which could be reviewed by the Elias," NFL spokesman Michael Signora said. "In this case, the determination of Elias is that the fairest resolution is for the ruling of the on-site stats crew to stand."
The play in question occurred with just over a minute remaining in the first quarter of Denver's 34-14 win at Oakland on Sunday.
Remember that camera angles can be deceiving, depending on where the camera is located. But there were two angles that would back up whichever argument one wants to make.
Manning's pass clearly looks like a lateral in one camera angle. Another angle, from above, however, appears to show Decker gathering in the ball at the Denver 48-yard line with Manning about a foot deeper than that.
Manning finished with 266 yards passing before sitting out the second half, and his final throw was a 6-yard TD toss to Demaryius Thomas which gave him 5,477 yards for the season and also 55 TD passes, five more than Tom Brady's record set in 2007, considered a much more significant achievement that the single-season yardage mark.
With Denver safely ahead 31-0 at halftime and the home-field advantage throughout the AFC playoffs secured, Manning watched backup Brock Osweiler play the entire second half in his place.
Elias routinely reviews plays and often tweaks totals in the days following games, then notifies teams of corrections to totals such as yardage or sack numbers.
Manning broke the TD record two weeks ago at Houston and was all smiles afterward, crediting his coaches and teammates and saying it was a significant mark that meant a lot to him because it came in the midst of a successful season. The Broncos (13-3) are the AFC's top seed in the playoffs for the second straight season. They have a bye this weekend and will host a divisional round game Jan. 12.
He was much more nonchalant about the yardage record.
Had the play in question originally been ruled a lateral, Manning would have finished the first half six yards shy of Brees' record of 5,476 yards, and that might have prompted the Broncos to send him out to start the third quarter even with the big lead and the playoffs looming.
Then again, maybe not.
Coach John Fox demurred when asked Monday if he would have considered sending Manning out for another series after halftime if he hadn't already broken Brees' mark.
"That's hard to say. ... What was very positive was I thought we played, if not our best, one of our better halves of football that put us in a position where we could do different things," Fox said. "No. 1, all those things are great, those individual accomplishments, team accomplishments, but not at the risk of putting a player at risk. So I don't know if I've answered your question, I'm just kind of telling you what would go through our minds in that situation."
After breaking Brady's TD record, Manning said he expected Brady to break the mark again soon, adding that all sorts of marks will fall like dominoes if NFL owners get their way and expand the regular season from 16 to 18 games.
Had Elias' ruling gone the other way, his yardage record wouldn't have even lasted 48 hours. Now, it'll stand for at least a year and maybe much longer.