Mattison (undisclosed) won't practice Wednesday, Dane Mizutani of the St. Paul Pioneer Press reports.
Mattison has been sidelined with an undisclosed issue since Aug. 23. With less than two weeks remaining before the Vikings' Sept. 12 season opener in Cincinnati, Mattison's status will warrant close monitoring. With Kene Nwangwu (knee) also not practicing, starter Dalvin Cook is currently the only healthy running back on the Vikings' roster.