Castro, who injured his right knee stepping awkwardly on first base in Wednesday's game against the Tigers, flew to Houston on Thursday and was scheduled to have surgery at 7:30 a.m. CT Friday. The procedure will be performed at The Methodist Hospital by team medical director Dr. David Lintner.
It's unknown how long Castro will be sidelined, but he remained optimistic as he left Osceola County Stadium and headed to the Orlando airport.
"There's nothing that can change it," he said. "I'm trying to stay positive and really looking to start the rehab process and get back to playing."
2010 Spring Training - null
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Spring Training Info
Quintero appeared in 88 games last year as the backup, and Towles was the Opening Day catcher a year ago, but was sent to the Minor Leagues and missed most of the year with a finger injury. Non-roster invitee Carlos Corporan could get more playing time.
"I feel sad for him, because I know he's working hard," Quintero said. "We have a good relationship, me and him. We worked together last year. I feel really sad that happened to him. He was going to be the starting catcher. He's a good kid and I hope he's going to be back soon."
Astros general manager Ed Wade said he likes the catching depth in camp.
"It falls on the other five guys in camp, particularly Towles, Quintero and Corporan to step up and show what they're capable of doing," he said. "The good news is we have a little bit of depth here in camp, and J.R.'s played well down here. It's still early, but he's swung the bat well and moved around real well and caught a good game [Wednesday] against the Yankees.
"One of the reasons we signed Corporan was we felt he had the ability to move back and forth between Triple-A and the big leagues if an emergency occurred, and this could qualify as an emergency. We'll wait for word from the doctors, evaluate what we have in camp and proceed accordingly."
Wade said he'd be open to bringing in another catcher to add to the mix.
"We always look to try to improve the club if we could," he said. "If there's an opportunity to do something, we'd be open to it. It's so early right now, so we'll just have see what."
Castro has been keeping the knee on ice and was taking anti-inflammatory medicine to keep the swelling to a minimum.
"I'm feeling OK," he said. "It's a little stiff. I'm up and walking around and stuff and still have a hard time kind of straightening it a little bit. There's no real sharp pain or anything, so that's always a good thing."
Castro, the team's first-round pick in 2008, came to Spring Training entrenched as the starting catcher after getting 195 at-bats in his Major League debut a year ago. He hit .205 with two homers and eight RBIs, but the club was impressed with how he handled himself behind the plate.
After a stellar career at Stanford, the Astros took him with the eighth overall pick in the 2008 First-Year Player Draft. He moved steadily through the organization, hitting .287 in 215 career Minor League games, before being called up last June 22.
Brian McTaggart is a reporter for MLB.com This story was not subject to the approval of Major League Baseball or its clubs.