SANTA CLARA, Calif. -- San Francisco linebacker De'Vondre Campbell refused to enter Thursday night's game in the third quarter after losing his starting job when Dre Greenlaw returned from an injury.

Campbell had started 12 of the first 13 games of the season and played 90% of defensive snaps for the 49ers but was benched for San Francisco's 12-6 loss to the Los Angeles Rams after Greenlaw came back for his first game since tearing his left Achilles tendon in last season's Super Bowl.

Greenlaw had eight tackles in the first half but left the game in the third quarter with soreness in his Achilles tendon. That's when Campbell refused to enter the game.

"He said he didn't want to play today," coach Kyle Shanahan said after the loss, which left the 49ers (6-8) on the brink of playoff elimination.

Shanahan said he has never seen that before in his coaching career and said the team will "figure out something" on how to deal with it going forward.

Campbell walked to the locker room, leaving his teammates bewildered and angry.

"He's a professional," cornerback Charvarius Ward said. "He's been playing for a long time. If he didn't want to play he shouldn't have dressed out. He could have told them that before the game. I feel like that was some selfish s--- that he did. It definitely hurt the team. Dre went down and we needed a linebacker. ... For him to do that, that's some selfish stuff to me in my opinion. He's probably going get cut soon."

The 31-year-old Campbell signed a one-year, $5 million deal in the offseason with San Francisco after being cut by Green Bay in March.

He had been an All-Pro in 2021 for the Packers but his play fell off the last two seasons in Green Bay. He had a few bright moments in San Francisco this season but struggled frequently with tackling and in coverage.

"It's one person making a selfish decision," tight end George Kittle said. "I've never been around anybody that's ever done that and I hope I'm never around anybody who does that again."