Mattison (illness) was placed on the reserve/COVID-19 list Monday.
Mattison reverted to a complementary role Week 14 versus the Steelers with Dalvin Cook back on the field, and he's now entered COVID-19 protocols. According to Tom Pelissero of NFL Network, Mattison tested positive for the virus. Veteran tailback Wayne Gallman was claimed off waivers to bolster Minnesota's depth at running back in the meantime.