"It's sore," the third baseman told MLB.com about his back, which has a bulging disk and has kept him out of the lineup since July 4. "It might be just because I hadn't hit for three days and that's the reason. I don't know."
"I'm not going to hit [Sunday] -- let it calm down and see how it feels."
Polanco still planned to accompany the Phillies to Chicago after Sunday's game, and has not scheduled a revisit to the doctor.
"No, I have seen a lot of doctors," he said.
Plan B, if rest and oral medication did not ease the problem, had been an injection, but Polanco reported back from the All-Star break saying he felt "90 percent" and never took the shot.
Asked if he was worried, Polanco said:
"Yes, a little bit. You're always worried, because you just want to come back and play.
He was 0-for-15 before the All-Star break and was hitting only .183 since injuring his back in Toronto on June 4.
The Phillies have used both Michael Martinez and Wilson Valdez at third in Polanco's absence. Martinez was hitting second in the lineup in Sunday's series finale against the Mets.