The 49ers have four quarterbacks on their roster, but only two dressed Thursday night.
Kurtis Rourke left after Patrick Taylor's 1-yard touchdown run with 8:38 remaining in the first half. Rourke might have been injured two plays earlier on a 3-yard run.
He went into the sideline medical tent before walking to the 49ers' training room with members of the team's medical staff.
The 49ers announced that Rourke has a rib injury and is questionable to return.
Adrian Martinez has replaced Rourke and presumably will finish the game.
Rourke went 12-of-14 for 100 yards and ran for 14 yards on three carries.
The 49ers also saw cornerback Jack Jones leave with an injury. He is ruled out with a right hand injury.
More info on: Jack Jones, Kurtis Rourke