SAN FRANCISCO (AP) — Barry Zito had a tough act to follow.

Pitching less than 24 hours after Matt Cain threw the first perfect game in Giants history, Zito was unable to keep the ball in the park. He allowed two home runs, one a grand slam, and San Francisco failed to complete a sweep, dropping the series finale 6-3 to the Houston Astros on Thursday.

Zito (5-4) lasted five innings, allowing five runs and five hits. He walked three and struck out three in losing two straight decisions for the first time this season.

“I screwed up making pitches and things happened after that,” Zito said. “I can improve on a lot of things.”

After tossing 8 1/3 shutout innings against the Chicago Cubs on June 3, Zito has allowed nine runs and 14 hits over his last 11 innings.

“He was throwing the ball well,” Giants manager Bruce Bochy said. “He allowed a solo home run and then got out of sync.”

Brandon Belt hit a two-run homer and Hector Sanchez added a sacrifice fly for the Giants, who are 12-5 over their past 17 games.

“They trust me out there and I’ve played well against anyone they’ve put on the mound,” Belt said. “That makes you feel comfortable in every at bat.”

J.D. Martinez hit his first career grand slam, Matt Downs also homered and Justin Maxwell drove in a run for the Astros, who had dropped 13 of their previous 17 — including a 10-0 loss Wednesday night in which Cain tossed a perfect game. Jose Altuve had two hits and walked as the second baseman continues to rank among the major league leaders in average and hits.

“We had to bounce back today and we had to get runs early,” Downs said. “Altuve set the tone early and got it over with. That pumped all of us up.”

Wandy Rodriguez (6-4) went six innings to win his third straight decision, allowing three runs and six hits. Brett Myers worked the ninth for his 16th save in 17 opportunities.

Zito walked Altuve, Brian Bixler and Jed Lowrie in succession to open the third, setting up Martinez’s slam that traveled halfway up the bleachers in left field. He has allowed four home runs in his past two games after allowing four in his previous eight.

“He was making some mistakes, falling behind hitters and walked three guys,” Martinez said. “I knew he had to give me something to hit. That was my mindset. I was going to be aggressive and go for it.”

Belt’s third home run in as many days put the Giants on the scoreboard in the fourth. His two-run shot cleared the bleachers in right and landed in McCovey Cove for the team’s 61st “splash hit.”

Sanchez hit his sacrifice fly in the sixth.

NOTES: Giants 1B Aubrey Huff underwent an MRI to assess damage in his bruised right knee, injured while jumping over the railing following the conclusion of Cain’s perfect game. ... Martinez broke a 12-at-bat hitless streak with his slam. He has 13 RBIs in 10 games against the Giants. ... Giants IF Joaquin Arias extended his career-best hitting streak to eight games. ... Altuve recorded his 28th multi-hit game. ... Martinez hit two grand slams at Double-A last year.