SAN FRANCISCO -- Astros catcher Jason Castro was placed on the disabled list on Sunday with right knee effusion, the lingering result of surgery he underwent last year.

Castro was placed on the disabled list retroactive to July 8, so he will be eligible to return on July 23, and he said it's reasonable to think he will be back that quickly because the injury isn't serious.

"I've been told this is somewhat normal for coming off the surgery I've had," said Castro, who had surgery to repair a torn ACL in March 2011.

He said he had felt some swelling over the past week and it just wouldn't subside. Castro said he could hit, but couldn't catch.

Castro is hitting .254. He had started 49 of the Astros 88 games at catcher.

The Astros purchased the contract of catcher Carlos Corporan, and he was in the lineup for Sunday's game against the Giants. Corporan was hitting .273 at Triple-A Oklahoma City, including 12 hits in his last 25 at-bats.

The Astros moved right-hander Kyle Weiland (shoulder) to the 60-day DL to make room on the 40-man roster for Corporan.

Lowrie heads to DL, back to Houston for tests

SAN FRANCISCO -- Jed Lowrie, the Astros' shortstop and No. 3 hitter, was placed on the disabled list on Sunday with ankle and knee injuries.

Lowrie, who was hurt in a collision at second base on Saturday against the Giants, was set to return to Houston for a further evaluation that would determine how long he might be out.

The Astros said Lowrie has a sprained right ankle and an injury to the peroneal nerve in his right knee.

"We'll let the doctors look at him and we'll know more then," manager Brad Mills said.

Marwin Gonzalez was activated from the disabled list to take Lowrie's spot on the field and on the roster. Mills said Gonzalez will get the bulk of the playing time at shortstop.

Lowrie was still walking with the aid of crutches when he arrived at the ballpark on Sunday. He reported to trainers that he felt "a little bit better, but not a whole lot," Mills said.

Lowrie was trying to make a force at second in the third inning on Saturday night. He was stretching to take a throw from second baseman Jose Altuve when Giants outfielder Gregor Blanco slid into Lowrie's leg. Blanco's foot pinned Lowrie's leg, and he injured his ankle and knee stretching.

Lowrie has 14 homers, second most among National League shortstops to Washington's Ian Desmond, who has 17. His .343 on-base percentage is tops among NL shortstops.

Gonzalez had been on the disabled list because of a bruised right heel. He was hitting .333 at Triple-A Oklahoma City on his rehab assignment.

Brian Bixler, who replaced Lowrie when he left Saturday's game, may also get some time at shortstop, Mills said.

Lopez returns to bullpen with a flourish

SAN FRANCISCO -- Perhaps lost amid the details of a disappointing 12-inning loss on Saturday night, the Astros enjoyed an encouraging return for right-handed reliever Wilton Lopez.

Lopez, who had been out for a month with a right elbow sprain, pitched two scoreless innings against the Giants.

"It was outstanding to see him come back and throw the ball like he did," manager Brad Mills said Sunday. "That was definitely a bright spot."

Lopez threw 29 pitches, so he was not available on Sunday. Mills said having Lopez back in the Houston bullpen helps solidify the entire group.

"Sometimes roles get overplayed a little bit, but when you get an arm like that you can slot into your bullpen. That's pretty nice," Mills said.