Mattison is in the league's concussion protocol Monday, Alec Lewis of The Athletic reports.
Mattison left Sunday's game against the Saints in the third quarter and never returned to action. With Cam Akers (Achilles) already done for the rest of the season, the Vikings will be left with Ty Chandler, Kene Nwangwu and practice-squad members Myles Gaskin and DeWayne McBride in the backfield if Mattison is unable to play Week 11 against the Broncos.