DETROIT — After a pair of promising carries looked to set the stage for a huge performance, San Francisco 49ers running back Raheem Mostert departed Sunday’s game against the Detroit Lions with a knee injury and will not return.

Mostert carried twice for 20 yards on San Francisco’s second possession but headed to the sideline soon after a 9-yard gain on the second play of the series. Rookie running back Elijah Mitchell stepped in for Mostert and had a 38-yard touchdown run on the series after Mostert’s injury.

The Niners initially announced that Mostert was questionable to return, but he was ruled out with an official announcement early in the third quarter. Mostert spent the rest of the first half on the bench without a helmet on as Mitchell and fellow running back JaMycal Hasty picked up the running back snaps.

Mostert is coming off an injury-plagued season, playing in eight games last year as a knee sprain and a high-ankle sprain cost him two and six games, respectively. He averaged 5.01 yards per carry in the eight games he played in 2020.

Rookie running back Trey Sermon, whom the 49ers drafted in the third round this year, is also on the roster but was a pregame inactive Sunday against the Lions.