Indianapolis Colts running back Marlon Mack suffered a hamstring injury in Indianapolis' preseason opener against the Seattle Seahawks on Thursday night. Mack, a second-year player, got the start at running back Thursday. It was unclear when he suffered the injury. Mack rushed four times for 9 yards and had two receptions for 23 yards, including an 18-yard reception off a swing pass on Andrew Luck's first pass of the game. It was Luck's first play in 585 days.