SAN FRANCISCO — San Francisco Giants left-hander Noah Lowry will undergo arthroscopic surgery Tuesday on the back of his elbow to remove bone spurs, another setback for someone expected to be a key member of San Francisco's rotation this year.

The 27-year-old Lowry has spent the entire season rehabilitating from a March 7 operation to repair a rare nerve problem in his forearm called exertional compartment syndrome.

Lowry had been on a throwing program in Arizona and was close to pitching in the Arizona instructional league. He also had been scheduled to pitch in winter ball, though that is now doubtful. Still, the Giants will head into the offseason with Lowry in their plans to be part of the rotation come 2009 barring further setbacks.

The recovery time for Lowry's surgery, which will be performed by Dr. Lewis Yocum, is expected to take about six weeks. Lowry underwent an MRI exam earlier this week and was examined by Yocum, who discussed the results with Giants orthopedist Dr. Ken Akizuki and then surgery was recommended to the club and Lowry.

"We're being optimistic that we can count on him and that the surgery will clear up everything and give him peace of mind," manager Bruce Bochy said Friday before the Giants opened a weekend series with the rival and newly crowned NL West champion Los Angeles Dodgers. "Hopefully it's the last step to getting him recovered so we can count on him in the rotation. That's going to be our thinking going into the winter."

Lowry had hoped to return in mid-April from his forearm procedure, but was still experiencing tingling in his throwing arm. He led the Giants with 14 wins last season and has a 40-31 record with a 4.03 ERA in 106 career games.

Lowry was a first-round draft pick by the Giants selected 30th overall in 2001. He is signed through next year with a club option for the 2010 season.