Rizzo (back) was participating in drills ahead of Monday's game against the Padres, Jordan Bastian of MLB.com reports.
Rizzo was participating in agility/running work in the outfield Monday, and he later started taking grounders at first base. The 31-year-old has missed the last five games due to back stiffness, but he could return to game action Monday if he feels good after his pregame warmups.