Ty Wigginton was slotted as the Phils' starting third baseman Sunday.
It was previously believed that Polanco's injury was a sore left knee, but the veteran third baseman said before Sunday's game that it was actually his ankle that was sore. He hopes to play Monday against the Nationals. He pinch-hit in Saturday's 7-5 loss to Boston.
"When I run, I feel it. It's sore," Polanco said. "But it's getting better. It's getting better, and it's a day-to-day thing."
Polanco said he's "almost 100 percent sure" the injury stems from one of the foul balls he recently hit off his ankle. He left Wednesday's game in Chicago in the seventh inning after fouling off a ball.
Polanco, who last week recorded his 2,000th career hit, is hitting .279 with eight RBIs this season.