Baldelli, 26, has been sidelined since last May because of lingering hamstring problems and has appeared in just 127 of 486 games the past three seasons because of an assortment of injuries. He has played in two games this spring, going 0-for-4 as a designated hitter.
Baldelli will be sidelined indefinitely, but said Wednesday that he is not retiring. He said there hasn't been an exact diagnosis but that doctors have told him he has "some type of metabolic and/or mitochondrial abnormalities."
"Basically somewhere along the line ... either my body isn't making or storing ATP the right way, therefore not allowing my muscles to work as they should, and especially recover like they're supposed to on a day-to-day basis," Baldelli said.
Last year, he played in 35 games before hurting his hamstring running out a grounder on May 15. He aggravated the injury after just two games of a rehabilitation assignment with Triple-A Durham in June, and the Rays shut him down for the season in August, when lingering soreness ruined his comeback bid after two games with Class A Vero Beach.
The Rays had asked Baldelli to pace himself during spring training, hoping to keep him healthy and fresh for the start of the season. He said he felt fine when he reported to camp, but soon began regressing.
"My body is literally spent after a very short amount of time out on the field, which makes it extremely frustrating and difficult," he said, at times appearing on the verge of tears. "But it's something that's kind of a reality right now, something we're dealing with the best that we can."
The Rays sent him to several doctors during the offseason, hoping to determine why he has been unable to recover from what they initially believed was a routine hamstring injury. The decision to place him on the DL was made after the experts reached a consensus on Baldelli's condition.
"It's one of those things, unfortunately, that they can't diagnose 100 percent," Rays executive vice president of baseball operation Andrew Friedman said.
"There's a high confidence level that it is this. But we're still dealing with a little bit of an unknown. We're going to do everything possible from this day forward to continue to dig and figure out and try to identify exactly what it is and also how to treat it."
The Rays had been hoping Baldelli would be healthy enough to share right field and DH duties with Jonny Gomes and Cliff Floyd. The team has until April 1 to pick up a $6 million option on him for 2009 or exercise a $4 million buyout.
"While on April 1 we may decline the option, when the time comes we'll do anything and everything to make sure he's part of this organization," said Friedman, who is still hopeful that Baldelli will play again.
"We are all cautiously optimistic," Friedman said. "I don't have a medical reason to feel that way. But I know with Rocco's determination, our training staff with modern medicine the way it is, I just refuse to believe there's not a way we can figure this out."