Mason has 10 days to prepare for the 49ers' Week 7 matchup against the undefeated Kansas City Chiefs. If Mason isn't able to suit up, the 49ers will rely on rookie running back Isaac Guerendo and fourth-year running back Patrick Taylor Jr.

RB Jordan Mason, the NFL's leading rusher, suffered a sprained AC joint that is not considered serious during Thursday night's win at Seattle, but he will undergo further testing Friday.

Mason was off to a good start on Thursday night when he was tackled and immediately grabbed at his shoulder area in a game against the Seattle Seahawks. He stayed down for a while while athletic trainers tended to him. Mason went back to the locker room and the 49ers said he was questionable to return with a shoulder injury.