Mattison had 10 carries for 41 yards in Sunday's preseason win over Seattle.
With Dalvin Cook likely to sit out the entire preseason as the Vikings play it safe with their starting running back, Mattison has been the starter in the first two preseason games. His 4.1 YPC on Sunday were a positive sign as he could gain a significant role off the bench and emerge as the goal-line back. He looks set to win the No. 2 running back role.