PHILADELPHIA -- After waking up with pain in Milwaukee three weeks ago, Kevin Frandsen gutted it out as long as he could.

He played pretty well, too.

An MRI on Saturday revealed Frandsen had a stress fracture in his left fibula, something that built up over time. He says it's a "day-by-day thing," but he did not start the first game of Sunday's doubleheader against the Rockies. He will be reevaluated before Monday's series opener against the Marlins, assistant general manager Scott Proefrock said on Saturday.

"It all depends on how much I can play through," Frandsen said before Sunday's afternoon game.

Since his promotion from Triple-A Lehigh Valley on July 27, Frandsen has recorded multihit games in 12 of his 33 starts at third base. Overall, he's hitting .336 with three doubles, a home run and eight RBIs. His 37 hits in August tied for third-most in the National League.

His absence, coupled with Placido Polanco's season-ending back injury, leaves the Phillies thin at third base. Utility infielder Michael Martinez started at the hot corner for the second straight game in the first game of Sunday's doubleheader. Pete Orr, a September call-up from Lehigh Valley, is another option at the position.

"I just didn't feel like I was going to help the team at all," Frandsen said. "That's the main thing for me. It's not about myself. It's about we're trying to get something going. And if I'm going to be a hindrance to the team, then that's not going to be the right thing. When I'm ready to go and they're wanting me to play, then I'm ready to go."

Worth noting

• Reliever Raul Valdes was officially placed on the disabled list (retroactive to Aug. 31) before Sunday's game. Valdes will have arthroscopic surgery on the meniscus in his right knee on Monday.

• Jimmy Rollins's 17 home runs entering Sunday tie him for the team lead with Hunter Pence, who was traded to the Giants on July 31. Rollins has a chance to become the first Phillies shortstop to lead the team in home runs for a season.

• The playoff game between the R-Phils, the Phillies' Double-A affiliate, and the Trenton Thunder, the Yankees' Double-A club, was also rained out on Saturday night. The clubs will now play Game 4 at 4:05 p.m. ET on Sunday in Trenton. Adam Morgan was set to pitch for Reading, which trails the series, 2-1.

• Though manager Charlie Manuel had said he was considering giving Carlos Ruiz the start, Steven Lerud got the nod for the second game of Sunday's day-night doubleheader. It's Lerud's third Major League start.

• The pitcher of record in Sunday's afternoon 3-2 walk-off win, closer Jonathan Papelbon, earned his fifth win of the season, tying a career high set with the Red Sox in 2008 and 2010.