Lenoir has been inactive for the last three games, while Thomas has been inactive for five games this season, including three of the last four.
Thomas was a third-round pick in April's draft. The 49ers drafted Lenoir in the fifth round. If Norman can't go, one or both could see an uptick in their snap counts against the Rams.
The 49ers' other starting cornerback, Emmanuel Moseley, was a full participant in today's practice. He has been dealing with a neck injury but looks on track to play.