Rizzo was taking grounders at first base before the team's game on Saturday night in Pittsburgh against the Pirates.
The 25-year-old first baseman had a flare-up in his back in late August that prompted the decision to sit him. An MRI two weeks ago revealed a lower back strain that the doctor said would best treated if he sat out from all baseball activities for the next 10 days. Last week, he resumed those activities with some light hitting, fielding and running.
On the season, he is hitting .278 with 30 home runs and 71 RBI in his first All-Star season.
The Cubs sit in fifth in the NL Central.
- Marc Weinreich