Foster left Saturday night's game in the third quarter.
49ers middle linebacker Reuben Foster left Saturday's preseason game against the Colts with a concussion, the team announced.
During a play in the third quarter, Foster's head was landed on awkwardly. Foster left the field under his own power but immediately went to the team's medical tent.
San Francisco's final preseason game is only five days away, when it plays the Chargers on Thursday. Foster will need to clear concussion protocol in order to play.
If he is not cleared, Foster will not see playing time again until Week 3 of the regular season. In July, Foster was suspended for the first two games of the regular season for violating the league's conduct and substances of abuse policies.