The veteran reliever, a non-roster invitee, was seen early Saturday morning coming out of the clubhouse with his left arm in a sling. He injured his shoulder in an accident that occurred at the swimming pool at his house in Venezuela before his arrival to training camp.
"He had an accident a month ago getting out of a swimming pool," said Rays president of baseball operations Matt Silverman. "And it hadn't been checked out until he got here. It's going to push him back several weeks. We don't expect him to be ready for the beginning of the season. Probably won't throw for several weeks. ... But he's ready to rehab and get back as soon as possible."
The Rays' bullpen competition appears to be strong. Silverman was asked if he thought Belisario's absence would create a void.
"He was competing for a spot on the Opening Day roster," Silverman said. "We have a number of relievers in that same situation. So the competition will be even more fierce among a smaller group. But more than 40 guys are going to play on this club over the course of the year, and many of these relievers will get the chance, whether it's on Opening Day or sometime later in the season."
Belisario, 32, went 4-8 with a 5.56 ERA for the White Sox in 2014.
Belisario did not talk to reporters after Saturday's workout.
Bill Chastain is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.