The San Francisco 49ers have placed star running back Christian McCaffrey on injured reserve due to persistent calf and Achilles injuries, which will rule him out for at least four games.

McCaffrey missed the season opener, and after experiencing pain post-practice, he will remain sidelined. Last season, he was a standout performer, leading the NFL in yards from scrimmage and touchdowns.

In his absence, backup Jordan Mason excelled in a recent victory against the New York Jets and is expected to start again.