BOSTON (AP) _ Struggling Red Sox closer Keith Foulke had arthroscopic surgery to repair damaged cartilage on his left knee Thursday, the latest development impacting Boston's ineffective bullpen.

Foulke will begin rehabilitation immediately, and team doctor Thomas Gill said recovery from this type of surgery typically takes about six weeks.

The operation took place just hours before staff ace Curt Schilling was to pitch in relief for Triple-A Pawtucket with an eye toward joining Boston's bullpen. Schilling, on the disabled list since April 29 with an ankle injury, struggled as a starter in his last rehab outing for Pawtucket.

Red Sox general manager Theo Epstein has called Schilling's move to the bullpen ``short term.''

Foulke went on the 15-day disabled list on Wednesday. In his absence, the Red Sox could use Schilling, Mike Timlin and Alan Embree as closers. Timlin got the save Tuesday in Texas, and Embree earned one Wednesday against the Rangers.

In the past week, the Red Sox recalled Abe Alvarez from Pawtucket then sent him back when they called up Jeremi Gonzalez and Lenny DiNardo. On Wednesday, Scott Cassidy was promoted from Pawtucket.

Foulke, outstanding in last year's AL championship series and World Series, has struggled all season. He is 5-5 with a 6.23 ERA and 15 saves in 19 opportunities. In his last outing, Texas scored twice in the ninth inning for a 6-5 victory Monday, giving Foulke his second blown save in a week.

Last year, he was 5-3 with a 2.17 ERA and 32 saves in 39 chances. In the World Series sweep of St. Louis for Boston's first championship in 86 years, Foulke pitched in all four games _ earning a win and a save while allowing one run and four hits in five innings.