Coach Kevin O'Connell said after Sunday's 3-0 win over the Raiders that Mattison is dealing with a sprained ankle, Ben Goessling of the Star Tribune reports.
Mattison exited in the second half after racking up 66 rushing yards on 10 carries. His return timetable will hinge on the severity and location of the sprain, as low-ankle sprains often take no more than two weeks to come back from, while high-ankle sprains usually result in multi-week absences. Ty Chandler would be in line to handle the majority of snaps in Minnesota's backfield if Mattison misses additional time.