Mattison (rib) practiced fully Wednesday, Craig Peters of the Vikings' official site reports.
Mattison lasted just two offensive snaps in the Vikings' second preseason game before departing with the rib injury, and he's been sidelined from practice for most of the intervening period. Now that he's back on the field and uninhibited, he's set to serve as Dalvin Cook's primary backup for a third straight season. In the previous two, Mattison averaged 8.4 touches for 42.4 yards from scrimmage per game while scoring four touchdowns in 26 appearances.