Filling in for Peyton Manning. Facing Tom Brady — and a two-touchdown deficit in the fourth quarter.
None of it bothered Brock Osweiler.
The 25-year-old quarterback making his first career start in Denver felt right at home in the snow globe that was Sports Authority Field on Sunday night, where the Broncos handed the New England Patriots their first loss, 30-24 in overtime.
It all reminded him of his youth in Kalispell, Montana, where misfires in the backyard ended up in snowbanks "and you'd have to dust off all the snow," Osweiler said. "Fortunately, when you play in the NFL, there are guys on the sideline that dust off all the snow.
"But, yeah, it was fun."
Not for Brady, who lost yet another one of his trusted targets when star tight end Rob Gronkowski injured his right knee with 2:49 left in the fourth quarter on a clean hit by safety Darian Stewart and was carted off the field.
Brady's receiving corps already was depleted with injuries to Julian Edelman, Danny Amendola, Aaron Dobson and running back Dion Lewis. If Gronkowski's injury is serious, it could be the biggest loss of all.
"He's been through a lot, he's a tough guy," Brady said. "Hopefully, it's not too serious. All of our fingers are crossed."
Stewart swept in low, trying to break up the pass that fell incomplete.
"I hate to see it but it's really the only way for defenders to hit now," Brady said. "I bet if you ask a bunch of players they'd rather you go high than low. When you go low that's what happens. I don't think it's dirty. I just think it's the way football's being played now."
Gronkowski, who caught his ninth touchdown pass and led New England with six receptions for 88 yards before getting hurt, didn't speak with reporters afterward. He walked to the team bus with a slight limp but no brace and coach Bill Belichick said he had no update.
The Broncos (9-2) won it when C.J. Anderson bounced a run outside and raced 48 yards down Denver's jubilant sideline with 12:32 left in overtime after its top-ranked defense forced a three-and-out thanks to a big sack by Von Miller and a huge hit by Shane Ray.
Manning watched from the cozy indoors as his backup brought the Broncos back from a 21-7 fourth-quarter deficit and Denver handed the Patriots (10-1) their first loss since 2014.
New England's last loss was a meaningless 17-9 defeat to Buffalo on Dec. 28 before the Patriots won three games to claim another Super Bowl trophy and then swept through their first 10 this season.
Now, the Carolina Panthers (11-0) are the NFL's only remaining unbeaten team.
The Broncos never led until Osweiler threw a 3-yard touchdown pass to Bubba Caldwell with 1:09 left in regulation to put Denver ahead 24-21. But Brady needed just five plays to drive the Patriots 51 yards and into range for Stephen Gostkowski's 47-yard field goal with no time left.
New England won the coin toss and Denver's defense, which lost starters T.J. Ward and Sylvester Williams to ankle injuries on the same play in the first half, had to go right back out.
"It didn't look good at times," Broncos coach Gary Kubiak said, "but we figured out a way to get it done."
Anderson rushed for 113 yards and two TDs on 15 carries. Overall, the Broncos ran for 179 yards, particularly impressive given their double-digit deficit for most of the night and their 21-7 hole after Brady threw a 63-yard scoring pass to Brandon Bolden on the first play of the fourth quarter.
The Patriots managed just 39 yards on 16 carries.
Osweiler completed 23 of 42 passes for 270 yards with one TD and one interception on a tipped pass. Brady also was 23 of 42 for 280 yards with three TDs and no interceptions.
With Manning sitting this one out in a walking cast on his left foot, the greatest quarterback rivalry was put on hold — perhaps forever.
Instead of a 17th meeting between the QB greats, it was Brady versus Osweiler, which doesn't have the same Hall of Fame ring to it.
It still had plenty of panache.
Things looked bleak for the Broncos after Bolden's TD made it 21-7 and New England forced a three-and-out. But Chris Harper muffed the punt and Shaq Barrett recovered for Denver at the Patriots 36. That led to Anderson's 15-yard TD run. A short field goal pulled them to 21-17.
Then, Demaryius Thomas, who didn't catch any of the first 11 balls thrown his way, hauled in a 36-yard pass to midfield just before the 2-minute warning that ignited Denver's go-ahead TD drive.
"That's what great players do," Osweiler said. "No matter what happens in the first quarter, second quarter, third quarter or even early fourth quarter, big players step up in big times."
He easily could have been talking about himself.
Notes: Broncos RG Louis Vasquez left with a groin injury. ... Patriots LB Dont'a Hightower left with a knee injury. ... Ward and Williams were in walking boots post-game.
Follow AP Pro Football Writer Arnie Melendrez Stapleton on Twitter:http://twitter.com/arniestapleton