KISSIMMEE, Fla. -- Lance Berkman, who will undergo arthroscopic surgery on his left knee Saturday, is still aiming to be in the starting lineup for the Astros when they face the Giants to begin the season April 5.

Berkman will have surgery Saturday morning at Florida Hospital in Kissimmee to clean out debris that was a result of the contusion he suffered during one of the first day of spring workouts. He's expected to miss two to four weeks, though a better timetable will be known after the surgery, which will be performed by Dr. David Crumbie, with team medical director Dr. David Lintner present.

"I think any time you have a surgical procedure, you're always concerned about something unexpected or some sort of a complication, but I think the chances of that are minimal," Berkman said. "It's a pretty cut-and-dried procedure. I don't anticipate having any lingering effects from it. They said it's about a three-to-four-week recovery period, so I'm hoping it's closer to three weeks and I will be ready for Opening Day."

Berkman missed Houston's first Grapefruit League game with a knee contusion, but he played in the next five games and hit .364. He had the knee drained twice in the last week to remove fluid, but it remained swollen for several days. He was examined Friday morning by Lintner.

"It really wasn't getting any better," Berkman said. "It continued to swell up, so it's better to do this than have to worry about it jumping up in the middle of the season. I wasn't feeling great to begin with, so we were worried about it flaring back up. It never made any improvement."

Berkman had minor surgery on his left knee in 1999, and underwent surgery following the 2004 season on his right knee to repair a torn anterior cruciate ligament and missed the first few weeks of the season. If he's not ready to go on Opening Day, Geoff Blum would likely start at first base.

"We were hoping that it was something he could have gotten through non-surgically, but it makes sense at this point to get it cleaned out and have him move in a straight line when he is back on the field," general manager Ed Wade said.

Berkman, 34, doesn't expect a long recovery time.

"When you're younger than 35 from a biological standpoint, you're still recovering at the same rate you did when you were 25," he said. "I don't anticipate having any trouble. If I was 40, it might be a different deal. I feel pretty confident it's really a no-big-deal type thing. I want to get it behind me and move on."

Blum, who has played in more games with the Astros than any current player other than Berkman, played first base in 10 games last year. He hit .247 with 10 homers and 49 RBIs in 120 games, mostly at third base. Manager Brad Mills said Jeff Keppinger has been working out at first base, too.

"That's the beauty of March 12," Wade said. "We can spend the next number of weeks trying to get Lance ready for Opening Day, and if not, make the right decision going forward."

Berkman, 34, is arguably the Astros' best offensive player. He had a down season in 2009, but still hit .274 with 25 homers, 80 RBIs, 97 walks and an on-base percentage of .399 that ranked eighth in the National League. He's in the final year of a six-year, $85 million contract with a $15 million option for 2011.

Mills said he's somewhat relieved the knee issue will be resolved.

"I feel for him that he won't be able to make it," Mills said. "We'll be able to make do, but at the same time, you'd like a bat like that and a player like that in your lineup. But at the same time, I'm kind of relieved a little bit that it's all going to be taken care of. If we just miss him for two weeks, that will be good."

Berkman was diagnosed with a knee contusion March 2, and Wade said Berkman wouldn't have been able to undergo surgery for a few days anyway had the diagnosis been made sooner because he had suffered a strawberry rash on the knee from sliding.

"Dr. Lintner said until the strawberry was healed, it would have been inappropriate to do surgery and risk infection," Wade said. "He said that it's looking good right now to proceed with the surgery. We really didn't lose any time in the process by trying to navigate non-surgically."

Lintner also examined right-hander Alberto Arias on Friday and diagnosed a right shoulder strain. He will try to throw Saturday and could get a cortisone shot.

"I'm happy now," Arias said. "It's just inflammation. I was thinking it might have been my rotator cuff. It's not a [big] problem."