SAN FRANCISCO -- Brad Lidge is hopeful that the discomfort in his right knee isn't a serious issue, but he'll find out soon enough after he's examined by team doctors Wednesday.

Lidge was scheduled to fly to Houston in the morning and is expected to rejoin the team in Arizona on Thursday.

"He won't pitch today, probably won't [Wednesday]," general manager Tim Purpura said prior to Tuesday's game in San Francisco. "It would make sense to get it checked out. I'm cautiously optimistic. It's not something that came on after a slip and fall or anything like that. It just came on slowly."

Lidge had been feeling discomfort in his knee for about a week and suspected the pain may be due to loose cartilage.

"If I had to take a guess, that's what I would say," Lidge said. "There was no ugly football injury where my knee bent backward to tear the MCL. I don't think it's anything bad. Right now, it definitely has a lot of discomfort."

Lidge has been able to play through any lingering pain, but as he warmed up during Monday's game, "it started biting me really bad," Lidge said.

A setback couldn't come at a more inopportune time. Lidge is in the middle of one of his best stretches since he was removed from the closer's role in April, having recorded scoreless outings in 13 of his last 16 appearances.

"It's frustrating right now, but if it's only something minor, it's OK," he said. "You get bumps and bruises throughout the season, that's fine. If it's something major, that will be frustrating, because I feel really good right now and I feel like I'm in a really good place as far as throwing goes. It would be frustrating if I had to miss a chunk of time larger than just a couple days."

Early BP: Following Monday's shutout loss to the Giants, hitting coach Sean Berry recruited Lance Berkman, Morgan Ensberg and Jason Lane to take a few rounds of early batting practice for an hour Tuesday afternoon. Brad Ausmus also asked to participate.

"I try to get everybody out there, especially guys who aren't playing that much," Berry said. "Then there are times like last night where I said, 'All right, why don't you come out?'"

Berry acknowledged that Berkman, who entered Tuesday's game hitting an uncharacteristically low .265 on the year and has only six extra-base hits, is pressing.

"When things aren't falling for you, it's human nature," Berry said. "When you're not getting hits, you start trying to do too much. He'll be fine. He's too talented for him not to be. He just has to grind his way through it and somehow try to relax, during this time that he feels like he has the weight of the world on his shoulders."

Biggio rests: Craig Biggio was omitted from the lineup Tuesday, the first of what will likely be two days of rest during the current road trip. Biggio is also scheduled to be off Sunday in Arizona, which, coupled with Monday's off-day, will give him two days in a row to rest.

"Two days for me is big when you can get it," Biggio said.

Third baseman Mike Lamb led off Tuesday's game in Biggio's place, followed by Mark Loretta at second.

"[Lamb's] been doing a pretty good job getting on base," Garner said. "He had a little rough of a series against San Francisco [in Houston last week], but he's been doing a pretty good job getting on."

Race for the Pennant:The fifth annual Astros Race for the Pennant 5K Run/Walk and Junction Jack's Kids Fun Run will take place Saturday beginning at 7:45 a.m. CT at Minute Maid Park. Proceeds from the race will benefit the Astros in Action Foundation.

The course begins at Minute Maid Park on Texas Avenue, travels through downtown Houston and finishes inside the park. The first overall male and female runners in the 5K run each receive two round-trip airline tickets on Continental Airlines. Top male and female finishers in each race and age category receive a free pair of ASICS running shoes, compliments of Luke's Locker.

The top three male and female finishers in each age category receive a Houston Astros Family 4-Pack, including four caps and tickets to a 2007 regular-season home game at Minute Maid Park. Official race timing for the 5K will be provided using the ChampionChip. Junction Jack's Kids Fun Run is non-competitive -- all kids 12 and under will receive medals.

The Astros Race for the Pennant entry fee for the 5K Run/Walk is $22 before Saturday and $25 on the day of the race. The race entry fee for Junction Jack's Kids Fun Run (12 and under) is $16 before Saturday and $19 on the day of the race.

Registration forms are available on astros.com, in the Union Station lobby and the Fan Accommodations booths (Section 112 and 323) at Minute Maid Park and at a number of Houston-area sports and fitness businesses, including Luke's Locker at 1953 West Gray.

Coming up: The Astros and Giants wrap up their series on Wednesday at AT&T Park, beginning at 9:15 p.m. CT. Right-hander Matt Albers (1-3, 6.51 ERA) will face Giants lefty Barry Zito (3-5, 5.13).