PHILADELPHIA -- Continuing to work his way back from breaking the big toe on his right foot, outfielder Nate Schierholtz will begin a rehab assignment with Triple-A Lehigh Valley on Sunday.

Schierholtz said his understanding was that the assignment would last through Friday and he would return on Sept. 1, when rosters expand. The IronPigs play at home Sunday through Friday, with a day off on Tuesday.

Schierholtz had said earlier in the week he thought he would be ready by Tuesday, the first day he is eligible to come off the 15-day disabled list. He said his toe feels good enough for him to play right now, but it appears the Phillies want to take things slow.

Acquired from the Giants on July 31 as part of the Hunter Pence trade, Schierholtz hit .219 with a home run, a double and two RBIs in 11 games with the Phillies before fouling a ball of his toe on Aug. 12 vs. St. Louis.

Sore right knee keeps Brown from Phils' lineup

PHILADELPHIA -- A sore right knee kept Domonic Brown from Saturday's lineup, his first absence since July 31, the day the outfielder was promoted from Triple-A Lehigh Valley. Brown is day to day, manager Charlie Manuel said, and was possibly available to pinch-hit Saturday against the Nationals.

Brown, who came into Saturday's action hitting .273 with a home run, seven doubles and 11 RBIs in 24 games since his callup, told Manuel after Friday night's 4-2 win that his knee was bothering him.

"He might be in there [Sunday]," the skipper said. "We'll see where he's at."

In mid-June, when he was still with the IronPigs, Brown strained his right knee. It's unclear if his current soreness is related to that injury.

Utility man Michael Martinez started in right field in Brown's place on Saturday. Over his two seasons in the Major Leagues, Martinez has played 11 games in center field and one in left. Saturday was his first big league game in right field, though he did play there in Spring Training, Manuel said.

Polanco's ailing back keeps him on the bench

PHILADELPHIA -- The back problems that recently caused Placido Polanco to spend four weeks on the disabled list are still giving the veteran third baseman some trouble.

Polanco, not in the lineup for the fourth consecutive game, was not available to play on Saturday, Charlie Manuel said. Asked if there was any thought of putting Polanco back on the DL, the manager said, "We'll wait and see."

Polanco did take batting practice and fielded ground balls before Saturday's game against Washington.

"I talked to Polly [Friday] with [Phillies head athletic trainer Scott] Sheridan," Manuel said. "I tell him every time I talk to him, 'If you're hurting and playing definitely hurts you, it's also hurting your performance and it's not good for our team. It's not good for you, it's not good for our team.' That's kind of how I see it. In order for Polly to help us, then he has to get well. He has to be 100 percent. Unfortunately, he's missed a lot of time the last two years.

"He agrees. He says he doesn't want to go on the DL, but at the same time, we also need a player on the bench. If I send one guy to pinch-hit early, all of a sudden we're short on the bench. We need all 25 of our players. ... If it hurts him and it hurts his performance and it hurts him to play, then it's not good for him or us."

Lerud thrilled to have opportunity with Phils

PHILADELPHIA -- Around 2 p.m. ET on Friday, Steven Lerud walked into Double-A Reading manager Dusty Wathan's office and was told he was getting sent to Class A Clearwater. After going along with the joke for a bit, Wathan started laughing and told his catcher the real news -- Lerud had been promoted to the big leagues.

The real news came as a surprise for Lerud, who had never before made it past Triple-A. But when Brian Schneider went on the disabled list on Friday afternoon, the Phillies needed a catcher to back up Erik Kratz until Carlos Ruiz returns.

A non-roster invitee to Spring Training, Lerud said he never really envisioned an opportunity like this coming this year.

"It's a funny game," he said, smiling through an entire three-minute interview. "I've seen it happen before to other guys. Luckily, I was right place, right time, I guess. I put my dues in. I'm excited to be here."

Lerud, 27, hit .235 in 35 games for Reading, but recently assumed a backup role to Tommy Joseph, who was acquired from the Giants' organization in the July 31 Hunter Pence trade. In 2010, he played nine games with Triple-A Norfolk in the Orioles organization, but spent most of his time at Double-A Bowie. He also played in Bowie in 2011 before joining the Phillies' organization at Reading. "I worked hard down there just to kind of stay ready, just to play there," he said. "And you never know. That's what everybody always says. I hung in there and got this opportunity.

So what was it like when he walked into the Phillies' clubhouse for the first time on Friday?

"Pretty surreal," he said. "I still don't know if it's really set in for me yet. I still have to pinch myself a little bit to make sure that it's real. This was something I can't describe. Obviously, it's what you play for, and I'm pretty excited to be here."

Worth noting

• Carlos Ruiz caught Vance Worley's bullpen session on Saturday, the second session he's caught in the last three days. It's a positive sign for the injured All-Star catcher, who is progressing in his rehab from plantar fasciitis in his left foot. He had hoped to start running on Tuesday.

• Juan Pierre entered Saturday needing only one more stolen base to tie Maury Wills for 19th place all time. The veteran outfielder's 585 career steals are the most among active players. He came into the game with a team-leading 31 this season.