De'Vondre Campbell pulls a Diontae Johnson during 49ers TNF loss to Rams

The San Francisco 49ers lost, 12-6, to the Los Angeles Rams on Thursday Night Football. It feels like the sort of loss that defines a season. Not much has gone right for San Francisco since its fateful Super Bowl loss back in February. Rather than defending their NFC crown, the Niners are scrapping hard just to stick in the Wild Card picture.

We can blame the elements or the fatigue inherent to a Thursday night football game — not to mention the ongoing spate of injuries dragging this Niners team down — but this loss was inexcusable, despite all the obvious, easy excuses. The Niners' defense did its job against a spritely Rams offense, but San Francisco couldn't move the football at all.

This was an awful Brock Purdy game, an even worse Deebo Samuel performance, and somehow, and even worse Jauan Jennings outing. Pretty much nobody except George Kittle showed up and the Rams' defense took advantage. San Francisco finished with a grand total of 191 yards of offense.

What happened to the Kyle Shanahan we know and love?

Perhaps the biggest storyline from this game, however, was a Niner who didn't play — and not because he was hurt. In the third quarter, veteran linebacker De'Vondre Campbell apparently told Kyle Shanahan that he didn't want to enter the game and left for the locker room.

Shanahan was blunt in his postgame assessment.

49ers LB De'Vondre Campbell channels Diontae Johnson with refusal to enter TNF loss

This comes a little more than a week after Diontae Johnson refused to enter a game for the Baltimore Ravens, which earned him a one-game suspension. It's an epidemic, apparently, and a strange one at that. Frustration is understandable given how this Niners season has gone, but quitting on your teammates mid-game — when the Niners were actually in a position to win — is baffling. This wasn't exactly a Rams blowout.

Campbell's teammates were far less forgiving. Charvarius Ward wondered why the 31-year-old even showed up to begin with, and proclaimed, "he's probably gonna get cut."

There's really no coming back from this for Campbell. It has been a less-than-ideal season for the former Pro Bowl linebacker, but this is the nail in the coffin. The Niners just can't afford this attitude, lest their season slip away. San Francisco needs to rally under pressure and fight to salvage its season — not crumble and quit when things don't go well.

One can't help but notice the timing of Campbell's revolt. Fellow OLB Dre Greenlaw made his first appearance of the season on Thursday, which naturally cut into Campbell's reps. Greenlaw spent the last 10 months rehabbing an Achilles injury and made his triumphant return against the Rams. Campbell, evidently, did not take kindly to the sudden competition for snaps.

This is a bummer and an unnecessary stain on Campbell's reputation, not to mention a 49ers team that doesn't need any more negativity circling the locker room. We shall see if Campbell is actually cut or just suspended, but the hammer will drop eventually. Probably sooner than later.