Mattison (ankle) isn't participating in Thursday's practice, Ben Goessling of the Minneapolis Star Tribune reports.
Despite sitting out the Vikings' Week 15 win over the Chargers, Mattison still is hobbled by the ankle injury he picked up during the Dec. 8 victory over the Lions. Courtney Cronin of ESPN.com notes that Mattison was at least able to work with a trainer off to the side, though he didn't do any running or jogging. Mattison will have two more days to fit in some practice activity and improve his outlook for Monday's game against the Packers, but as things currently stand, both he and lead back Dalvin Cook (shoulder) seem to be in danger of missing the divisional showdown. Mike Boone took the reps with the first-team offense Thursday and is in line to headline the Vikings' backfield Week 16 if Cook and Mattison can't go.