‘Key matchup: Niners’ RB Christian McCaffrey vs. Bills run defense. Buffalo bottled up the Chiefs in limiting their ground game to 78 yards in a major sign of improvement a month after allowing 271 to Derrick Henry and the Ravens. McCaffrey and the 49ers’ usually sturdy run game has yet to get on track, with last season’s offensive player of the year limited to 149 yards rushing and 132 receiving, while yet to score a TD in three games this season.’