Stacy enjoyed an excellent rookie campaign last season, rushing just shy of 1,000 yards and scoring seven touchdowns on the ground.
However, Schottenheimer has claimed that third-round 2014 Draft pick Tre Mason is pushing Stacy all the way to start in the team's backfield.
"Right now, competition is for who's the starter," Schottenheimer told reporters. "We're just going to let them all roll and see what happens.
"Zac's obviously a really, really good player, but we're going to create competition for all the guys. We know we have a good stable group of backs and they all have different skill sets, which we'll try to use throughout the course of the year."