HOUSTON -- Already short-handed at catcher, the Astros lost starter Jason Castro early in Monday's game against the Twins.
Castro was pulled from the game after an RBI single in the second inning with a sprained right knee -- the same knee he had surgically repaired in 2011. This injury, suffered while he was running the bases in the first inning, isn't believed to be serious because Castro left the ballpark without the aid of crutches or wearing any kind of brace.
The Astros will update his condition after he's seen by a team doctor on Tuesday.
"Obviously, they're going to give us their best evaluation, and then we'll talk to Jason and go from there," manager Bo Porter said.
Castro, an All-Star this season and two-time American League Player of the Week, is having a career season, hitting .282 with 18 homers and 56 RBIs after going 2-for-2 with two RBIs on Monday.
The Astros have two catchers on the seven-day concussion disabled list -- Carlos Corporan and Max Stassi. Corporan was injured Aug. 19 when he took a foul ball of his facemask, and Stassi was hit in the head by a pitch two days later and hasn't played since.
Cody Clark, a 31-year-old who was called up Aug. 23 after 11 years in the Minor Leagues, replaced Castro and went 0-for-3, dropping him to 0-for-13 for the season. The Astros didn't call up a third catcher when rosters expanded. Their Triple-A affiliate in Oklahoma City and Double-A affiliate in Corpus Christi are both going to the playoffs.
Brian McTaggart is a reporter for MLB.com and writes an MLBlog, Tag's Lines. Follow @brianmctaggart on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.