Juan Francisco was recalled from Triple-A Louisville to fill Cabrera's roster spot.
"I don't know," Reds manager Dusty Baker said when asked how long Cabrera would be out. "It has to be 15 days. That I don't know, I don't think anybody can answer that. That's a situation where I have seen guys come back in a period of time.
You just don't want him to try to rush and you end up re-injuring that thing and re-injuring it and re-injuring it. Because everything you do is related to your core unit, whether it's running, throwing, hitting, whatever."
Baker said Cabrera drove back to Cincinnati after the Reds' win over the Pirates at PNC Park on Monday and saw doctors on Tuesday.
Paul Janish batted second and started at short Tuesday against the Pirates, and he will likely remain there for as long as Cabrera is out.
"He's been very patient, he stays ready, he's been working hard," Baker said. "I told him a few weeks ago, 'Stay ready, because you never know what can happen.' And he trains hard, he works hard.
"And right now probably [Miguel] Cairo's my super utility man right now -- third, short, second, first. And we got Francisco probably [spelling] Scotty [Rolen] at third and trying to work out some at first base, too."
Cabrera was hitting .260 with 37 RBIs and 51 runs scored. Francisco hit .286 with 16 home runs and 53 RBIs in 67 games at Louisville.
Baker said the Reds' training staff will treat Cabrera's injury aggressively, adding that he has been surprised by the number of oblique injuries he has seen recently.
"You can do it getting out of bed, lifting something, so he has to be careful here. You see, it's kind of something that -- it's not new -- but you're seeing it a lot more in baseball now than I saw before," Baker said. "You're seeing pitchers get it, hitters get it. I bet if you checked it out, I bet it's one of the top injuries in baseball. Why? I don't know. It's usually weird to get it this late in the season, too, I think. You usually get it early.
"I know it was something bad though. You see the look on his face, he was in pain, big-time. I could just tell by the look on his face. ... I hope he caught it before it got too late."