Mattison (appendectomy) went through stretches and individual drills during the open portion of Thursday's practice, Eric Smith of the Vikings' official site reports.
Mattison's appearance at practice is his first since Dec. 4, as he required an emergency appendectomy a day later. The extent of the running back's participation Thursday won't be known until the Vikings release their second Week 15 practice report later in the day, but his presence on the field at least gives him an outside chance at returning from a two-game absence Sunday against the Bears.