Head coach Jim Caldwell won’t acknowledge his depth chart at running back, but on Saturday it was plain for everyone to see: Theo Riddick is the Detroit Lions’ starter, Tion Green is the backup and Ameer Abdullah has been regulated to third-string. Riddick played the vast majority of snaps at running back in the Lions' 20-10 win over the Chicago Bears before a wrist injury and a fumble ended his day. Riddick, making his third straight start, finished with eight carries for 49 yards and caught three passes. He fumbled on his final carry of the game just before halftime, which set up the Bears' first points,a 41-yard field goal by Mike Nugent. Riddick played just three third-down snaps in the third quarter, though Caldwell said he did not know if Riddick was injured on his fumble. "Some of the times it’s kind of difficult to tell (when a player gets hurt)," Caldwell said. "I mean, obviously he had some issues, surgery (on his wrists last year), so something may have popped up. Not certain of the extent of it as of yet, but we’ll take a look at it and see." While Riddick has emerged as the Lions' top running back, Abdullah remains in the doghouse in what's been a disappointing season.