The diagnosis was made on Friday before the team prepared to play its final spring training game against the Colorado Rockies in Phoenix.
On its Web site, the said that the 32-year-old left-hander, who was acquired in November 2006 and signed a three-year, $22 million extension with the club that runs through 2009, probably will make a couple of regular season starts before undergoing surgery.
"Obviously, we're all in his corner," said fellow pitcher Brandon Lyon. "We haven't gotten a chance to sit down and talk to him about it. All of us are just going to support him any way we can."
"Obviously, our thoughts and prayers are with him," said Manager Bob Melvin.
Team officials reserved comment on other details pending a news conference at a later time.