Mack is expected to miss a few weeks due to a hamstring strain, Jason La Canfora of CBS Sports reports.
Mack limped off the field during Thursday's exhibition at Seattle, but the injury isn't considered to be serious. With the Colts' expected No. 1 back out of commission, Jordan Wilkins, Nyheim Hines and Robert Turbin (suspension) will work with the first-team offense for the rest of the preseason.