ARLINGTON -- Astros catcher Jason Castro was placed on the injured list Sunday morning with a right knee injury. Manager Dusty Baker said Castro was being sent back to Houston to get the knee checked out while catcher Garrett Stubbs was en route from Triple-A to join the club.

Castro last started for the Astros on Tuesday against Kansas City, going 0-for-4. He played the final two innings on defense in Wednesday¡¯s series finale against the Royals and didn¡¯t see any action in the first two games of the Rangers series.

¡°It¡¯s the same knee he¡¯s had operated on three times, so he¡¯s got some symptoms, but there are so many structures in the knee that could cause these symptoms that we felt the best thing was to get him back there with our doctors ... get a scan, and see if we can ascertain exactly what¡¯s causing the symptoms,¡± general manager James Click said. ¡°Once we know that, we¡¯ll have a prognosis. At this point, it¡¯s too early to say.¡±

Castro has a history of right knee injuries, beginning in 2011 when he tore his ACL while running the bases in Spring Training and missed the entire season. He had a cyst drained from the knee in 2013, and he was limited to 19 games in 2018 after undergoing right knee surgery while with the Twins. He was on the IL earlier this year with left Achilles soreness.

¡°It was a chronic thing,¡± Click said. ¡°He¡¯s a veteran. He¡¯s very in-tune with this knee in particular, and he alerted us recently that the knee had been bothering him and after conversations, we decided this was the route.¡±

Castro has made 33 starts this year as Mart¨ªn Maldonado¡¯s backup and is hitting .190 with four homers and 13 RBIs. He¡¯s 5-for-15 as a pinch-hitter with three RBIs. Stubbs, meanwhile, is 4-for-22 in nine games with the Astros this year and was with Triple-A Sugar Land, which is playing in El Paso, Texas.