DENVER -- The Oakland Raiders are still heading to the playoffs but they're hurting, especially at quarterback.

Trevor Siemian threw touchdown passes to running back Devontae Booker and tight end Virgil Green, and the Raiders lost their starting quarterback to injury for the second straight week Sunday in a 24-6 loss to the Denver Broncos.

"We didn't do enough to earn a win tonight, and we didn't do enough to earn an opportunity to clinch the division. But we did earn our way into the playoffs," Raiders coach Jack Del Rio said. "So, it's huge for us to be able to pick ourselves up, dust ourselves off and get prepared for next week. You've got to be able to bounce back and move on and that's going to be priority No. 1 for us."

Booker caught a touchdown pass and also ran for a score in what was apparently Gary Kubiak's final game as Denver's head coach. Kubiak, who missed a game earlier this season because of a complex migraine condition and also suffered a condition akin to a mini stroke when he was coach of the Houston Texans, told players and staff after the game that he plans to retire.

Kubiak did not confirm the news during his post-game news conference but said he would discuss it publicly on Monday.

"Today is about the team and the players," Kubiak said. "I'll address my situation tomorrow."

Siemian said he was surprised by Kubiak's decision to step away.

"Kind of sad that he isn't going to be here," he said. "I didn't really have an idea. I'm glad we won but it just feels kind of weird."

In a frightening incident, the Broncos also lost linebacker Zaire Anderson to an injury suffered during a third quarter punt. As players from both teams looked on, medical personnel strapped Anderson to a stretcher, immobilizing his head before lifting him onto a cart and driving him to the locker room for further treatment. Kubiak said after the game that Anderson was expected to be all right.

The Raiders, who finished the game with third-string rookie Connor Cook at quarterback, lost their grasp on the AFC West title and the No. 2 playoff seed with Kansas City's win over San Diego. Oakland dropped to the No. 5 seed and heads to Houston next week to play the AFC South champions in a wild card game.

Quarterback Matt McGloin, making his first start since 2013, began the game as the replacement for Derek Carr, who is out indefinitely after breaking his right leg during the Raiders' victory over Indianapolis last week.

McGloin left the game in the second quarter after injuring his left shoulder. He apparently was hurt when defensive end Jared Crick hit him as he released a pass. McGloin was shaken up on the play and officials flagged Crick for roughing the passer for making contact with McGloin's helmet.

McGloin was ridden to the turf by Crick, who landed on top of him.

"My left arm just wasn't feeling good," McGloin said. "I couldn't throw in the motion that I was used to, my normal motion. I've got to be in there bright and early tomorrow and get treatment and get healthy."

Del Rio said it hasn't been decided whether McGloin or Cook would start next week.

"We've got to be able to move the ball to score points and we didn't move it very well and didn't score many points," Del Rio said. "Whether it's Matt or Connor, we need more productivity.

"We've got a good group of guys. We'll put together a good plan and get ourselves ready."

McGloin finished that series but was replaced by Cook, who saw his first NFL action after being inactive for the previous 15 games, for the Raiders' final offensive series of the first half.

Cook, who had an interception and one of the two lost fumbles by the Raiders, connected late in the third quarter on a 32-yard touchdown pass to Amari Cooper.

It was not enough to overcome the bounce-back performance by Siemian, who completed 17 of 27 for 206 yards after a subpar performance in last week's loss to Kansas City that eliminated last season's Super Bowl winners from playoff contention.

Siemian's 2-yard scoring pass to Green midway through the third quarter put Denver up 24-0. The scoring drive began after defensive end Adam Gotsis recovered a fumble by Cook and was aided by a pass interference penalty against the Raiders that set the Broncos up with a first-and-goal situation.

Clearly feeling the loss of Carr and stung by the shoulder injury that sidelined his replacement, the Raiders fell behind Denver 17-0 at halftime.

The Broncos, who had scored only two touchdowns in their three games, marched 84 yards in its opening possession under Siemian and Booker finished the drive with an 11-yard touchdown run.

Running back Justin Forsett broke loose on a 64-yard run -- the longest rush by a Broncos player this season -- to set up Brandon McManus' 22-yard field goal before Booker turned a short pass in the left flat from Siemian into a 43-yard touchdown with 1:44 remaining in the second quarter.

NOTES: Broncos WR Emmanuel Sanders left the game in the first quarter with a foot injury. He did not return. ... Raiders S Karl Joseph missed the game with a toe injury. It was the fourth consecutive game missed by Joseph, who was replaced in the starting lineup by Nate Allen. Allen was sidelined in the second quarter with a concussion. ... Denver DE Derek Wolfe (neck) and S T.J. Ward (concussion) were among the players designated inactive by the team. ... Oakland DT Stacy McGee sat out with a groin injury. Darius Latham started in his place. ... Booker became just the seventh Broncos' rookie and the first in 15 years to have a rushing and receiving touchdown in the same game.