Jimmy Garoppolo underwent knee surgery Wednesday

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49ers quarterback Jimmy Garoppolo underwent surgery Wednesday morning to repair a torn anterior cruciate ligament in his left knee, coach Kyle Shanahan said, via Matt Maiocco of NBC Sports Bay Area.

Shanahan did not know whether the surgeon found other damage to Garoppolo’s knee. He added it was too early to know Garoppolo’s rehab schedule.

Garoppolo injured his knee in a Sept. 23 game against Kansas City as he planted his left foot near the sideline.

The 49ers placed Garoppolo on injured reserve three days later and promoted Nick Mullens from the practice squad to back up C.J. Beathard.

Beathard threw for 298 yards with two touchdowns and two interceptions in the loss to the Chargers.