MILWAUKEE -- Pirates outfielder Brandon Moss will have knee surgery next Friday that will keep him from playing 4-6 months, possibly longer, general manager Neal Huntington said last night at Miller Park.

The procedure, known as a microfracture, will address bone-on-bone friction in the left knee due to of a lack of cartilage, but it will be performed by Dr. Richard Steadman, the same doctor who examined Moss in Vail, Colo. In a microfracture, tiny holes drilled into the knee to allow room for cartilage to regrow naturally.

"We're not going to have a firm idea of length until Dr. Steadman gets in there and sees what's inside," Huntington said. "Right now, we're hoping to have him back early next spring."

The positive, Huntington said, is that Steadman's preliminary diagnosis showed enough cartilage currently there that all parties seriously entertained the idea of not having the surgery at all. But it was decided, to preserve Moss' future, to go ahead with it.

Steadman's opinion seconded the original diagnosis of Dr. Patrick DeMeo, the Pirates' team physician, earlier in the week.

Huntington described the condition as being more common in basketball than baseball and cited the example of NBA standout Amare Stoudemire of the Phoenix Suns as a positive: Stoudemire had a microfracture Oct. 18, 2005, and, though he missed the final five months of that season, has been healthy since.

"Basketball players' knees take a much greater pounding, and they're having a lot of success with it," Huntington said. "If this had been 10 years ago, it might be a much bigger problem. As it is, with this being caught early and while the player was still really symptom-free, the chance of preventing this from becoming something that worsens over time is very good."

So, the question arises: Did the Pirates get damaged goods when acquiring Moss from the Boston Red Sox as part of the July 31 Jason Bay trade?

Huntington said yesterday that the Pirates had no knowledge of Moss' knee issue until an end-of-season physical in which Moss informed DeMeo. The initial thought, based on symptoms in the physical, was that the meniscus was the problem, which would have been minor. But an MRI ordered by DeMeo revealed the lack of cartilage.

Moss acknowledged two days ago to reporters that he had trouble with the knee prior to the July 31 trade with the Boston Red Sox. Moss recalled feeling discomfort while playing on artificial turf in American League stadiums, though he was adamant he had no trouble while playing for the Pirates.

"We had no indication it would be something like that. None," Huntington said.

Huntington added that there was no information on the knee in the medical records the Pirates reviewed from the Red Sox before the trade.

"Again, no indication."

No physical was performed by the Pirates, but Huntington said that "typically is the case" before trades. Most often, the team reviews existing records, he added. That position is corroborated by others in the industry.

There is no sign of any kind of action being mulled against the Red Sox. If any were taken, it is extraordinaly unlikely that anything would come of it. Generally, Major League Baseball reviews injury issues related to a trade immediately or very soon after the trade. It has been nearly two months in this case.

Scott Boras, agent for top draft pick Pedro Alvarez, said yesterday that his estimate of the total added value to his client's revised, four-year, $6,355,000 major league contract was an additional $1 million, based on a projected career path of Alvarez reaching Pittsburgh within two years.

His estimate under the original -- a $6 million bonus and minor league contract -- was that it would pay $7.2 million over the same span that the new one would pay $8.2 million.

The Pirates' stance, as made clear by team president Frank Coonelly, is that, because the revised bonus is staggered over four years rather than two, the net present value of the guaranteed amount dropped to $5.67 million because of appreciation and interest. That figure is based on Alvarez spending all four years in the minors.

• Outfielder/first baseman Jamie Romak, who hit 25 combined home runs for Class A Lynchburg and Class AA Altoona, will be the final player assigned by the Pirates to the Arizona Fall League. Now, all spots in Arizona and Hawaii are filled.

• The highest-ranking Pirates official present at Alvarez's signing Wednesday at PNC Park was scouting director Greg Smith.

• Ronny Paulino, buried on the bench with just three pinch-hit at-bats following his Sept. 2 recall, started behind the plate for the first time since May 31. Expect Ryan Doumit to catch all three in San Diego.