Indianapolis Colts running back Marlon Mack is once again dealing with an injury and has been ruled out of Sunday's game against the Miami Dolphins, according to Andrew Walker of the team's official site.
Adam Schefter of ESPN reported Mack was evaluated for a concussion after coming out of the game.
The running back had made a significant impact before the injury, rushing for 85 yards on 15 carries and making two catches for 11 yards.
Health problems have held Mack back all season. A hamstring ailment limited him to one appearance in the Colts' first five games, and foot and ankle injuries have also bothered him.