Mack (hamstring) "might come down to the wire" for Week 1, according to Andrew Walker of the Colts' official site.
The running back suffered his hamstring injury back on Aug. 9 and though he's made "good progress," per coach Frank Reich, Mack's Week 1 availability is not considered a slam dunk. In the event that he isn't ready for the Colts' Sept. 9 contest against the Bengals, Jordan Wilkins profiles as the frontrunner to start in his place.