He threw in a simulated game Monday but threw only 12 pitches before having to leave the mound.
The operation was performed by Dr. James Andrews in Birmingham, Ala. Howell is expected to recover in time for the 2011 season, the Rays said.
Howell recorded 17 saves and a 7-5 record in 69 appearances for Tampa Bay last season, but had not played this year.
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