GOODYEAR, Ariz. (AP) -- Chris Perez couldn't finish his first bullpen session without trouble.
Cleveland's All-Star closer will miss at least one month and possibly six weeks with a strained left side muscle he injured throwing off the mound for the first time in spring training.
It's the second significant injury in camp already for the Indians, who announced Friday that center fielder Grady Sizemore will not be ready for opening day because of a strained lower back.
Trainer Lonnie Soloff said Sunday there's still a chance Perez will be ready for opening day on April 5.
"I wouldn't say that," Soloff said when asked if Perez will miss the opener against Toronto. "We'll have to see how things go and how he responds with his throwing sessions once he gets back on a mound."
Soloff said Perez will need four to six weeks to recover and the hope is the hard-throwing right-hander will be able to pitch in games "toward the end" of the exhibition season.
Perez, who had 36 saves in 40 chances and a 3.32 ERA in 64 games last season, got hurt during the latter stages of his workout.
"His body was clearly not ready for the intensity of that bullpen session," said Soloff, who was asked if he meant Perez was not in shape.
"No," he said. "I'm just saying he wasn't prepared for the intensity of the bullpen session."
Because he's a reliever and not a starter needing to build stamina, Perez will not need as much time to get ready for the start of the season. If there's a bright side to his injury, that's it.
"Definitely a positive," Soloff said.
Soloff suggested that Perez may have gone too hard his first time off the mound and any player needs to "know thyself" when working out.
"He's learned," Soloff said.
If Perez winds up not being available for the opener, set-up man Vinnie Pestano would be manager Manny Acta's likely first option to close.
Acta has said there are two bullpen jobs up for grabs this spring.
