Wide receiver Emmanuel Sanders, who has been with the 49ers for just three games after a trade with the Denver Broncos, left the game with a rib injury and is listed as "questionable" to return.
Sanders left for the 49ers locker room at Levi's Stadium with 8:20 remaining in the first half of play.
He isn't the only player injured in the game.
Defensive tackle D.J. Jones is "questionable" to return due to a groin injury, and starting center Weston Richburg is having his left hand examined by the 49ers' medical staff. He was replaced by Ben Garland.
Update: Richburg went to the 49ers locker room to undergo an X-ray on his hand.
Update 2: Richburg has returned to the game. Sanders and Jones have been downgraded and ruled "out."