Dempster, on the disabled list since June 16 with a sore right lat, said Friday he's making progress.
"It won't take me long once I get going," Dempster said. "I haven't said [I'm returning on] 'This date' because if I feel good, it could be sooner than that. I'm completely pain free. I just don't know how I'm going to feel throwing."
Randy Wells subbed for Dempster for two starts, but he was designated for assignment on Wednesday. The Cubs need another starter Tuesday against the Braves, and manager Dale Sveum said the options include Casey Coleman, who is currently in the bullpen, and Chris Volstad, who is pitching for Triple-A Iowa.
Volstad was sent to Iowa after opening the season 0-6 with a 7.46 ERA in eight starts with the Cubs. In eight starts at Iowa, Volstad is 2-3 with a 4.44 ERA, giving up 25 earned runs on 59 hits and 12 walks while striking out 41 over 50 2/3 innings.
Coleman was starting at Iowa at the beginning of the year but has been used strictly out of the bullpen with the big league team. On Wednesday, he gave up seven runs on six hits over 1 2/3 innings in relief.
The good news for the Cubs is that Dempster is indeed close to returning. The right-hander was 3-3 with a 2.11 ERA in 12 starts before he got injured, and he had not given up an earned run over 22 innings while winning his past three starts.
"Everything's been on schedule as far as what we're trying to do," Sveum said of Dempster. "Obviously, there's no timetable for anything yet."