The Pirates removed Andrew McCutchen from the lineup Sunday because of pain in his right knee.
McCutchen approached the Pirates' coaching staff after taking batting practice Sunday morning to inform them of the discomfort.
"[He] had right knee soreness and he wasn't comfortable," manager Clint Hurdle said.
McCutchen said he thought the pain originated Thursday when he slid into home plate against the Milwaukee Brewers.
"I didn't feel anything at the time, but I think that's something that caused my uncomfortable feeling," McCutchen said.
Hurdle said the Pirates' medical staff checked McCutchen's knee and "he felt better about the situation."
"Just wanted to make sure everything was OK," McCutchen said. "I feel like I can play through whatever, but I didn't want to jeopardize the rest of the season playing through something I wasn't comfortable about."
McCutchen had started 42 of the Pirates' 43 games this season before Sunday.
Starling Marte, who originally had Sunday off so he could have two days of rest in a row, started in center field. Travis Snider started in left, Garrett Jones in right.
Jeff Karstens will make his next rehabilitation start Thursday, though the Pirates have not yet decided where.
Karstens completed four innings in his rehab start Saturday with Class AA Altoona and threw 60 pitches. He allowed 2 runs, both unearned, on 2 hits, 2 walks and 4 strikeouts.
"They dropped the ball on him in the first inning, which extended the pitches," Hurdle said. "He got through four, pitch-efficient after the first, got in a good rhythm, threw all four pitches. It was a good outing."
James McDonald, who like Karstens is on the disabled list because of a shoulder problem, will throw bullpen sessions Tuesday and Friday. The Pirates have planned his first rehab outing May 27, when he will throw four innings or 65 pitches for Altoona.
Grilli leads majors in saves
Jason Grilli saved his 17th game Sunday afternoon, giving him the most in the majors. New York Yankees closer Mariano Rivera is second (16).
"You can't back away from the job Jason's doing at the end of the game," Hurdle said. "Jason continues to just stay on the accelerator, make pitches, mix speeds. It's hard, it's soft, there's spin, there's a changeup. He slide-steps. He's been very, very effective and very, very precise."
Grilli has recorded those 17 saves in 192/3 innings. He has allowed 2 runs on 9 hits and struck out 31 batters and walked 4.
Out at home; no complaints
The Astros threw out Travis Snider at the plate by several feet Sunday to hold the Pirates to a one-run lead.
Snider doubled in the sixth, and Gaby Sanchez singled to center with two outs. The ball was hit right at Brandon Barnes, who fielded it cleanly, but third-base coach Nick Leyva waved Snider home. Barnes' throw beat Snider to the plate, and Carlos Corporan held on as Snider tried to run over him. The two exchanged a fist bump, and the inning was over.
"I liked the fact that we pushed the envelope on a play at the plate," Hurdle said. "We were thrown out. They made a baseball play."
Bill Brink: email@example.com and on Twitter @BrinkPG. First Published May 20, 2013 4:00 AM