The Associated Press

SAN FRANCISCO - San Francisco Giants closer Robb Nen will undergo arthroscopic surgery on his ailing right shoulder Friday in Los Angeles.

Nen has been on the disabled list since opening day. The surgery will be performed by Dr. Lewis Yocum.

The operation was recommended Wednesday after Giants orthopedist Dr. Gary Fanton conferred with Yocum. Nen spent most of spring training rehabilitating his right shoulder after undergoing the same procedure in November.

Nen is the Giants' career leader in saves with 206. He has 314 saves in his 11-year career.

RED SOX: The team purchased Jason Shiell's contract from Triple-A Pawtucket and optioned right-hander Bob Howry to Pawtucket.

Howry gave up 11 hits and six runs in four games for a 12.46 ERA. Ramiro Mendoza, who blew a 5-1 lead Tuesday before Shea Hillenbrand's game-winning single in the bottom of the ninth, has a 16.71 ERA after seven appearances.

YANKEES: Closer Mariano Rivera reported no problems Wednesday, one day after throwing 40 pitches in batting practice.

Rivera is on the 15-day disabled list with a right groin strain and is expected to pitch one inning in an extended spring training game Friday.

SHORT HOPS: Since a 15-2 opening-day loss to the Cubs, Mets starter Tom Glavine has allowed only two runs over 18 innings in three starts, a 1.00 ERA. The victory was the 244th of his career.

• Montreal's Vladimir Guerrero will donate 100 tickets to fans from his home country of the Dominican Republic for each of the Expos' three Sunday games in Puerto Rico. The tickets will help create "La Esquina de Vladimir" - his own rooting corner behind him in right field - for games against Cincinnati, Texas and Florida.

• The Brewers are 0-8 in day games, and 1-5 at Miller Park.