In this Oct. 27, 2012, file photo, South Carolina running back Marcus Lattimore (21) rushes up field after taking the hand off from quarterback Connor Shaw, back, during an NCAA college football game against Tennessee in Columbia, S.C. Lattimore has informed the San Francisco 49ers he plans to retire two years after a devastating knee injury. The team made the announcement Wednesday, Nov. 5, 2014, two days after coach Jim Harbaugh said Lattimore was weighing his football future.(AP Photo/Richard Shiro, File)

Janie Mccauley

SANTA CLARA, Calif. (AP) — Running back Marcus Lattimore has informed the San Francisco 49ers he plans to retire two years after a devastating knee injury.

The team made the announcement Wednesday, two days after coach Jim Harbaugh said Lattimore was weighing his football future.

The 23-year-old Lattimore, San Francisco’s 2013 fourth-round draft pick, practiced last Wednesday and Thursday but not Friday. He was eligible to return after Week 6, but Harbaugh says Lattimore had doubts his knees would allow him to play at the NFL level long term after serious injuries to both.

He spent his rookie season last year on injured reserve after tearing major ligaments in both knees during college at South Carolina. The serious knee injuries derailed his 2011 and ’12 seasons before the Niners took a chance on him in the draft anyway. He underwent surgery for a torn anterior cruciate ligament in his left knee in 2011.

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