Christian McCaffrey downgraded to out with knee injury

49ers running back Christian McCaffrey will not return to Sunday's matchup against the Bills. McCaffrey has been downgraded to out with the knee injury he suffered in the first half. McCaffrey exited the contest in the second quarter after he took a pitch to the right, took a few slow steps, and slid down to give himself up. He was examined in the sideline tent before heading up to the locker room for further examination. He had rushed for 53 yards on seven carries and caught two passes for 14 yards before exiting.McCaffrey missed the first eight games of the season with bilateral Achilles tendinitis. Jordan Mason has been San Francisco's leading rusher with McCaffrey sidelined.San Francisco also ruled out defensive tackle Kevin Givens.While the 49ers advanced to the red zone on their opening drive of the second half, Kyle Juszczyk fumbled inside the 5-yard line with Buffalo recovering and returning it to the 48-yard line.