"We'd love Reuben to be on this team," York told Matt Maiocco of NBC Sports Bay Area. "And we'd love him to participate for us, but if he's not doing things off the field that allow us to be able to rely on him - or he's doing something that we're not comfortable with off the field and it's proven that's what's going on - I think the guys have said then you're just going to have to move on."
Foster, a former first-round draft pick, has been involved in multiple incidents away from the gridiron over the past year. He was arrested in January for possession of marijuana, and in February for domestic violence. The district attorney's office hasn't decided whether to pursue charges against Foster for the latter incident.
"We have to wait until that (decision) happens, but that will obviously be something that we get together and discuss whatever comes down when those issues come up and figure out where we move from there," said York.
The 23-year-old second-year linebacker posted 72 tackles in 10 games as a rookie, but York made it clear he won't make many more in a San Francisco uniform if he doesn't clean up his act.
"From my conversations with (general manager) John (Lynch) and (head coach) Kyle, I know Reuben is very cognizant of where his position is right now, and his time with the 49ers could potentially be over if he continues to do things outside of the team that aren't what we want him to be a part of," he said.