Indianapolis • Indianapolis Colts running back Robert Turbin has been suspended without pay for the first four games of the season for violating the NFL policy on performance-enhancers.

The NFL announced the suspension Friday. Turbin is eligible to participate in offseason and preseason practices and games.

Turbin, who played at Utah State, tweeted that a urine sample he provided to the league resulted in a positive test. Turbin said he was “truly sorry” for “a mistake that will not only have personal consequences, but will affect the Colts organization, an organization that I am extremely appreciative to be a part of.”

The 28-year-old Turbin played six games and ran for 53 yards and a touchdown on 23 carries last season before getting placed on injured reserve Oct. 20.