New York Mets right-hander Paul Blackburn underwent a procedure to repair a cerebrospinal fluid leak earlier this month and will be sidelined at least four-to-five months, the team announced Tuesday.The surgery was performed by Dr. Wouter Schievink on Oct. 11 at Cedars-Sinai Medical Center in Los Angeles.Blackburn, 30, landed on the 15-day injured list with a bruised hand on Aug. 25. The Mets shut him down in mid-September after the leak was discovered. At the time, the team said it didn’t believe it to be a long-term problem.