Steelers quarterback Ben Roethlisberger said it's unrealistic to expect a lot from newly-signed running back Ben Tate in Saturday's playoff game against the Ravens.

“I don’t know how you could come in in a couple of days and learn a new offense,” Roethlisberger told ESPN.com. “I think if we can put together a specific package, a few runs here, a few passes there, I think he could help us if we need him to.”

If starter Le'Veon Bell (knee) can't play, rookie running back Josh Harris would start and be spelled by rookie Dri Archer and Tate. Harris, an undrafted free agent out of Wake Forest, rushed five times for 7 yards Week 17 but had a 59-yard run called back on a penalty.

The Steelers are 3-point home favorites.