SAN FRANCISCO -- Astros catcher Jason Castro was unavailable for the first two games of the series against the Giants because he's been feeling discomfort in his right knee, which he seriously injured last spring.
"It slowly built and built and when we were on the break it kind of hit a peak," said Castro, who tore his ACL and had surgery in March 2011.
The Astros may need to make a decision on Castro because if he's unable to catch they have no backup for Chris Snyder, who caught all 12 innings on Saturday night and withstood a jarring home-plate collision on Friday.
Castro said he's not sure whether he'll be able to play on Sunday, for the finale of the series against the Giants.
"It's a day-to-day thing," he said. "It felt better at certain points today than the day before. We just have to watch it on a daily basis."