"That was just precautionary last night, just to let it calm down a little bit," Castro said before Friday's game. "It's been better today. Been getting treatment. Once the swelling gets out of there, I should be ready to go. We'll see how it responds to the treatment, but I'm pretty optimistic."
Castro said he could play again as soon as Saturday.
"It's about as day-to-day as you can get," Castro said. "If I wake up [Saturday] and it's feeling good, I could get other there tomorrow."
Carlos Corporan started at catcher for the Astros Friday night with outfielder-first baseman Marc Krauss the emergency catcher. Krauss said he had not caught in a regular game since his senior year of high school in Deshler, Ohio.
"It's been a while," Krauss said. "I caught for seven years, from Little League all the way through high school."
Krauss said he had offers from a couple Mid-American schools to play catcher in college. Instead, he went to Miami of Ohio where he played outfield and first base.
"I've been doing drills in Spring Training," Krauss said of practicing as a catcher. "We'd get out early with the catchers, catch balls from the machine, work on some of the fundamentals."
Krauss said he enjoyed working out behind the plate again.
"I missed it," he said. "I had fun catching. You're always in the game. It's exciting, but it's a lot of hard work. I don't miss the hard work."
And what if Krauss had to put on the gear Friday night?
"I'd definitely be nervous," he said. "If you don't do your job, you'd let the team down. But I would also be excited. I spent a long time back there. I hope it doesn't get to that point."
Castro thought Krauss could do the job, if necessary.
"I was pleasantly surprised," Castro said of watching Krauss work out behind the plate in spring.