Shanahan told reporters that the 49ers were working out the details of Campbell's departure following his actions in Thursday's 12-6 defeat against the Rams at Levi's Stadium.
Campbell was dropped from the starting line-up to make way for the returning Dre Greenlaw in Thursday's game. However when asked to go on during the third quarter, Campbell refused and walked off to the 49ers locker room.
The game ended in a defeat that almost certainly snuffed out San Francisco's chances of reaching the postseason.
"His actions from the game are not something you can do to your team or teammates and still be a part of our team," Shanahan said Friday.
"We're working through the semantics but we'll handle the situation accordingly."
Campbell's team-mates lambasted his conduct, with star tight end George Kittle describing the linebacker as "stupid and immature."
"I've never been around anybody that's ever done that and I hope I'm never around anybody that does that again," Kittle said.
"It's just dumb. It's just stupid. It's very immature," Kittle said. "I just don't see how you could do something like that to your team."
Niners cornerback Charvarius Ward was equally scathing, predicting that Campbell would be cut by the club.
"He's a professional. He's been playing for a long time. If he didn't want to play, he shouldn't have dressed out," Ward said.
"For him to do that, that's some sucker stuff to me. He's probably going to get cut soon."
