Mack, who has been dealing with a hamstring issue since Aug. 9, is "trending in the wrong direction" as Sunday's season opener against the Bengals approaches, Kevin Bowen of 1070 The Fan Indianapolis reports.

Given that Mack is a player reliant on speed more so than power, it's expected the Colts will ease him into the mix once he's ready to practice, whenever that might be. If Mack is sidelined this weekend, Jordan Wilkins, Christine Michael and Nyheim Hines would serve as the team's backfield options in Week 1. Of that group, Wilkins would be the presumed starter.