Conteh is listed as out on Northwestern's injury report after getting hurt at Wednesday's practice. The senior started last week against Minnesota after leading rusher Tyrell Sutton suffered a dislocated wrist that will keep him sidelined for the rest of the regular season.
Conteh's injury, which occurred during a noncontact drill, is not considered season-ending.
Wildcats sophomore Stephen Simmons is expected to make his first career start at running back. Simmons has four carries for 19 yards this season. He had a 99-yard kickoff return for a touchdown last year against Ohio State.
"While we're disappointed for Omar, we're excited for the next man's opportunity, in this case Stephen Simmons, Jacob Schmidt and Scott Concannon. Our players are prepared to step up and fill in at running back," Northwestern coach Pat Fitzgerald said.
Senior quarterback C.J. Bacher is probable for the Ohio State game after sitting out last week with a right hamstring injury.
Fitzgerald said this week that Bacher would start against the Buckeyes if healthy, but junior Mike Kafka also will be part of the game plan after a strong performance in relief against Minnesota.
Adam Rittenberg covers the Big Ten for ESPN.com. He can be reached at firstname.lastname@example.org.