It was hardly unthinkable that New England's undefeated season might come to an end against Denver.
But for it to happen like this? With an injured offense making plays and a stout defense coming undone? That was a shocker.
Playing without their two top receivers, and then without tight end Rob Gronkowski in overtime, the Patriots blew a two-touchdown lead in the fourth quarter then squandered a game-saving drive by Tom Brady.
They gave up a 48-yard touchdown run in overtime and fell 30-24 to the Broncos. Now, instead of looking for perfection, they'll need to keep winning to make sure any possible playoff rematch with the Broncos will come in New England, not Denver, where the snow fell for four quarters and then some Sunday night.
"We had a good lead, but we just didn't make a couple of plays in the fourth quarter," Brady said. "It's tough to win, and when you lose good players, it hurts. It always hurts to lose."
Brady finished with 280 yards and three touchdown passes. As always, he made due with what he had. He turned unheralded running back Brandon Bolden into a fantasy-football star, finding him behind linebacker coverage for a 63-yard throw and catch down the sideline that gave the Patriots a 21-7 lead early in the fourth quarter.
With the snow falling and with Brock Osweiler, making only his second career start, leading the Broncos nowhere, New England looked poised for 11-0.
Then, suddenly, the defense collapsed.
Osweiler led the Broncos on scoring drives of 36 and 52 yards to trim the deficit to four.
Then, most surprisingly, Osweiler led an 83-yard drive that gave the Broncos a 24-21 lead with 1:09 left. And nobody will say he picked on one single soft spot in the defense. He opened the drive with a 36-yard completion down the right sideline to Demaryius Thomas, who was singled up against Logan Ryan. Osweiler put the Broncos in scoring range with a 39-yard connection down the left sideline to Emmanuel Sanders, who beat Super Bowl savior Malcolm Butler one-on-one. Bubba Caldwell beat Ryan for the touchdown score, but still, the Patriots weren't done.
With Gronkowski lost to an injured knee, Brady moved the offense 51 yards in 69 seconds to set up Stephen Gostkowski's 47-yard field goal and send the game to overtime.
But after a quick three-and-out to start the extra session, the defense wilted quickly. After Osweiler's audible, C.J. Anderson went untouched around left end for the win.
"They started getting tired, and at this altitude, you can see it," Anderson said.
Only time will tell if being handed a loss, and leaving the pressure of the undefeated season to the 11-0 Carolina Panthers, will make things easier for the Patriots (10-1).
Either way, there will be no coasting. Denver (9-2) holds the tiebreaker and showed it can win with its young quarterback. In only his second career start, Osweiler threw for 270 yards and a score. Now, New England only leads the Broncos by one game in the standings.
There isn't much room for error for the Patriots. There is, however, plenty to correct.
"Could have coached better, could have played better," Patriots coach Bill Belichick said. "Guys played really hard and I have all the respect in the world for this football team and the way they competed."
One piece of good news: After being carted off the field, Gronkowski was seen walking out of the training room after the game with a slight limp. By appearances, at least, the knee injury was not serious.
Still, the flight back home won't be near as enjoyable as it could have been.
"We had plenty of opportunities," Brady said. "We'll try to get back to work this week."
Notes: Brady fell to 2-6 lifetime in Denver. ... Gronkowski led the Patriots with six catches for 88 yards followed by another tight end, Scott Chandler, who had five for 58. ... New England's Dec. 13 game against Houston has been moved to a night game. That's one of two games the Patriots have left against 6-5 teams. The rest of their future opponents have losing records.