Cabrera missed 27 games in August and September after pulling muscles in his side. He aggravated the injury during a 7-4 loss in Philadelphia on Friday night and had to leave the game. The injury bothers him most when he throws.
Cincinnati manager Dusty Baker said Cabrera was no better the next day.
"Not good," Baker said.
But Cabrera said later he was feeling better and was hoping to play.
"I do want to stay on the roster so I'm going to do everything I can to be able to run, play defense or whatever," he said.
The Reds have several players who didn't make the postseason roster working out at their spring training complex in Arizona, keeping them ready in case of injury. They brought infielder Chris Valaika back from Arizona on Saturday.
They'll decide before the game Sunday whether to replace Cabrera with Valaika, a move that would make Cabrera ineligible to play for the rest of the series and the NL championship series, should Cincinnati make it that far. The Phillies lead 2-0.
"He won't be eligible for the next round, but we've got to get through this round first," Baker said. "We'll see how bad he is first, but we need the player."
It would be a loss to the Reds in another way, as well. Cabrera was one of only three players in Cincinnati's starting lineup with playoff experience.
The left side of the Reds infield has been hobbled during the last two months. Third baseman Scott Rolen has been playing despite stiffness in his back and shoulders. He had an error -- one of four by Cincinnati -- that helped the Phillies rally from a 4-0 deficit Friday night.
Rolen has struggled in part because of the back problem. Since Aug. 1, he has only two homers and 21 RBIs. He's 0 for 7 with five strikeouts in the playoffs.
"It won't get well until winter time," Baker said of Rolen's back. "He's still a heck of a ballplayer and a heck of a threat. It's not like the guys facing us can't pitch, either. That compounds it."