Coach Frank Reich said Wednesday that Mack remains in the NFL's concussion protocol, Andrew Walker of the Colts' official site reports.
Reich didn't elaborate on whether Mack would take part in the Colts' first practice of the week Wednesday, but even limited involvement in that session would represent a sign of progress in the running back's recovery from the head injury, which forced him to exit in the fourth quarter of the Week 12 win over the Dolphins. If Mack is unable to pass through the five-step protocol in advance of Sunday's game against the Jaguars, Nyheim Hines and Jordan Wilkins would likely share the Colts' backfield snaps.