Dalton was injured on the fourth play of the third quarter after a snap by center Billy Price sailed over his head. Dalton ran back to recover the ball and attempted to pick it up, but the Browns recovered it. Dalton immediately went to the sideline and into the locker room with athletic trainers and did not return.
Dalton has not missed a game since the 2015 season when he attempted to make a tackle after throwing an interception against the Steelers and broke his right thumb. Although Dalton avoided surgery, he did not return that season, missing the final three regular-season games and the AFC wild-card game. AJ McCarron, who is now with the Raiders, replaced him.
Dalton was replaced on Sunday by quarterback Jeff Driskel. Dalton joins a long list of injured Bengals players, including wide receiver A.J. Green, who has missed the last several games with a toe injury.
Source : http://www.espn.com/nfl/story/_/id/25376035/bengals-qb-andy-dalton-leaves-thumb-injury