Mattison is starting in place of Dalvin Cook (ankle) on Sunday against the Seahawks, Eric Smith of the Vikings' official site reports.
Cook will sit at least one game due to the ankle sprain he picked up Week 2, allowing Mattison a spot start. When Cook went down with a groin injury Week 5 of last season in Seattle, Mattison put together the only 100-yard rushing performance of his career, totaling 112 yards on the ground and 24 more yards as a receiver. With just Ameer Abdullah and fullback C.J. Ham to contend with for touches, Mattison could be poised for another fruitful outing Sunday.