Jackson had six carries for 35 yards in Saturday's preseason loss at Buffalo.
Jackson had been sidelined in practice the past few days with a quad injury and wasn't expected to play. Apparently he's back to full strength, as he had some impressive runs while get the starting nod at running back. With top running back Jonathan Taylor (ankle) on the PUP list and Zack Moss out with a broken arm, Jackson could enter the regular season as the top running back. While the Colts may still decide to sign a veteran in that scenario (they were in talks with Kareem Hunt), Jackson gave them reason Saturday to feel confident he can handle the job, at least in the short term.