San Francisco 49ers running back Christian McCaffrey suffered an apparent non-contact knee injury early in the second quarter of Sunday night’s game against the Buffalo Bills.

After making a throw to the right side of the field at Highmark Stadium, McCaffrey suddenly pulled up and then settled into the backfield without making contact. It looked like something was pulling McCaffrey’s leg because he was seen limping a few steps before he simply slid down. He jogged off the field and a few moments later went into the blue medical tent on the sidelines.

McCaffrey was seen minutes later walking to the locker room under his own power with a team trainer. The 49ers initially said his return was questionable due to a knee injury. He had 53 rushing yards on seven carries and another 14 yards on two catches when he went out. Further details regarding his injury are not yet known and it is unclear whether he will be able to return.

McCaffrey missed the first eight games of the season in San Francisco due to Achilles tendonitis and calf strains. He even flew to Germany in September to receive treatment from a specialist after ending up on injured reserve. Sunday’s game was just his fourth of the season. He entered the night with 149 rushing yards and has yet to score a touchdown this year.

McCaffrey’s injury is the latest the 49ers have dealt with in recent weeks. They were without quarterback Brock Purdy due to a shoulder injury in last week’s loss to the Green Bay Packers, although Purdy started Sunday night. Nick Bosa and Trent Williams were also out on Sunday evening due to injuries. However, tight end George Kittle returned for the second straight game after missing earlier this month with a hamstring injury.

San Francisco entered Sunday’s game with a 5-6 record after losing two games in a row, which puts them in last place in the NFC West standings.

This post will be updated with more information shortly.