San Francisco 49ers head coach Kyle Shanahan gave an update on linebacker Reuben Foster on Monday. He did not seem optimistic that the rookie would return for the team's Week 5 contest against the Indianapolis Colts.

Foster has missed the past three games for the 49ers after suffering a high-ankle sprain during Week 1 against the Carolina Panthers. He is showing progress and started warming up and running with his teammates last week. When those teammates went on to participate in practice, Foster exited to a side field for rehabilitation.

"We'll see how his rehab goes these next three days," said Shanahan. "I'd be surprised if he got back this week. I'm not totally ruling him out but it would surprise me. I'm being optimistic about it but if we don't get him back this week, hopefully, we'll get him out there next week."

Matt Maiocco of NBC Sports Bay Area asked Shanahan if playing on turf this week had anything to do with Foster's timeline for a return.

"I don't think so," Shanahan answered. "When he's healthy, he'll be ready to go."