Carr completed just 12 of 29 passes for 135 yards. But two of his throws were for touchdowns, and the Raiders (6-7) beat the Broncos for the first time since Sept. 12, 2011 despite being held to minus-12 yards in the first half -- the worst performance by a team heading into halftime in nearly a quarter-century.
The Broncos (10-3) began the game as the AFC's top seed but couldn't finish drives, hold onto a 12-0 halftime lead or onto several on-target throws from Osweiler. Demaryius Thomas had two big drops, one for a touchdown and another for a late first down. He also lost a fumble.
The one that really stung was a drop by a wide-open Vernon Davis at the Oakland 42 on fourth-and-5 from the Denver 37 with 3:45 left.
"I got super excited because I knew I was going to be wide open, took my eyes off the ball and wasn't able to pull it in," Davis said.
Osweiler refused to blame his receivers for their many mistakes, his coaches for a conservative game plan, his running backs for gaining just 1.6 yards a carry, or his protection for getting him clobbered.
"No reason to point any fingers," said Osweiler, who completed 35 of 51 passes for 308 yards.
Mack's fifth sack helped snuff out Denver's final drive. Afterward, he said he counts this performance as sweeter than his big game at Ohio State in 2013 that cemented his first-round status because "this is the Broncos."
Mack said the Raiders knew they had a chance when they held the Broncos out of the end zone four times in the first half.
The Raiders drove 80 yards to open the second half and trim Denver's lead to 12-7 when Carr threw an 11-yard pass to Seth Roberts. A safety pulled the Raiders to 12-9 when Mack sacked Osweiler in the end zone and Broncos guard Max Garcia recovered the loose ball.
"He was unbelievable," Raiders coach Jack Del Rio said of Mack. "He's just getting better and better."
Oakland long snapper Jon Condo recovered Emmanuel Sanders' muffed punt at the Denver 11 early in the fourth quarter, but he injured his right shoulder in the pile. He was in the locker room getting it looked at when Carr threw a 16-yard touchdown pass to tight end Mychal Rivera to put Oakland ahead 15-12 with 14:26 remaining.
Without Condo, the Raiders went for 2 and Carr threw an incompletion, leaving the margin at a field goal.
Brandon McManus clanked a 49-yarder that would have tied it off the left upright with 10:22 remaining. Sebastian Janikowski then missed a 43-yarder with 5:07 remaining, giving the Broncos good field position at their 33, but Davis had his big drop on fourth down after that.
The Broncos couldn't get into the end zone in the first half despite 224 yards of offense, settling for four field goals from McManus, each one shorter than the previous -- 41, 35, 29 and 21 yards.
"We had a chance to really do some damage in the first half and didn't do it," Denver coach Gary Kubiak lamented. "And we obviously helped them in the second half with turnovers, I think four or five drops. We lost line of scrimmage offensively. We played great defense."
Oakland's lack of production in the first 30 minutes was the lowest figure by any team in the first half since Nov. 1, 1992, when the Chargers held the Colts to minus-5 yards.
Peyton Manning, missing his fourth straight start with a left foot injury, watched this one from the sideline after skipping the Broncos' trips to Chicago and San Diego and viewing Denver's win over New England from inside the locker room area.
"To have an extra set of eyes -- especially his eyes -- out there and helping me and coaching me through the whole situation is something that I appreciated," Osweiler said.
The Broncos sorely missed ramming running back C.J. Anderson, who was sidelined by an ankle injury, and once they had to keep throwing the ball, they couldn't block Mack.
"I remember playing Derrick Thomas my first game in the NFL against the Chiefs and he had six sacks against us," Oakland's 18-year veteran safety Charles Woodson said. "Today, Khalil kind of reminded me of that."
Darian Stewart (hamstring) is Denver's fourth injured safety. WR Cody Latimer and LB Lerentee McCray also pulled hamstrings. ... Raiders RT Austin Howard injured a knee early in the third quarter.
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