San Francisco 49ers running back Christian McCaffrey has been placed on injured reserve due to calf soreness and Achilles tendinitis, forcing him to miss at least the next four games. McCaffrey, who has not played this season, was a late scratch for the season opener against the New York Jets. Despite his absence, backup Jordan Mason performed well, rushing for 147 yards and a touchdown. McCaffrey's earliest possible return is for the Week 6 matchup against the Seattle Seahawks. Head coach Kyle Shanahan noted the injury's unpredictability, which led to the decision to place McCaffrey on injured reserve. This is McCaffrey's first IR stint since joining the 49ers in 2022.