The Indianapolis Colts are worried running back Marlon Mack suffered a torn Achilles in Sunday's season opener versus the Jacksonville Jaguars, sources told NFL Network's Tom Pelissero and Mike Garafolo.
The Colts ruled Mack out for the second half after being carted from the sideline to the locker room with what the team initially called an ankle injury.
Rookie Jonathan Taylor and Nyheim Hines are in position to lead Indy's backfield if Mack misses the remainder of the season.
Mack racked up 26 yards on the ground and three catches before exiting. The 24-year-old is scheduled to hit become a free agent at the end of the season.
