"We need to take a look at it," Tomlin said. "It's not good, of course, when a guy goes down in open grass not touched by anyone. Experience tells me that's generally not good."
Tomlin said Mendenhall would be evaluated when the team returns to Pittsburgh.
Mendenhall was injured on a 5-yard carry on the final play of the first quarter. He walked slowly to the sideline, where he was checked by Pittsburgh's training staff before heading to the locker room for further tests. He rushed for 38 yards on eight carries before leaving the game and was replaced by Isaac Redman.
The Associated Press contributed to this report