San Francisco 49ers running back Raheem Mostert announced Tuesday that he will be undergoing season-ending knee surgery.

Mostert took to Twitter to explain his decision:

The initial expectation was that Raheem Mostert was going to miss about half the season after suffering the knee injury in the Week 1 victory over the Detroit Lions. But after consulting with doctors, the 49ers running back has determined undergoing this surgery and missing the whole season is the best move to make for his career.

Mostert is no stranger to injuries. The running back only played in eight games last season, rushing for 521 yards and two touchdowns. He also caught 16 passes for 156 yards and a score.

This came after the best season of Mostert's career in 2019. The 49ers running back rushed for 772 yards and eight scores while averaging an impressive 5.6 yards per carry. San Francisco rode a dominant rushing attack and strong defense all the way to the Super Bowl, only to lose to Patrick Mahomes and the Kansas City Chiefs.

With this latest news, Mostert will have only hit double-digit games in three of seven seasons.

Looking past Raheem Mostert on the roster, rookie Trey Sermon was inactive for Week 1, but one has to think he'll get a chance to be active now. Elijah Mitchell and JaMycal Hasty jumped Sermon on the depth chart after the rookie was initially No. 2.

Furthermore, Jeff Wilson Jr. was already out, so the 49ers are bringing Kerryon Johnson to the practice squad, per ESPN's Adam Schefter.