HOUSTON — Clay Buchholz didn’t regret what pitch he threw to Colby Rasmus with the bases loaded in the fifth inning Saturday.

He just wished he had located it better.

Rasmus hit a tie-breaking grand slam to lead the Houston Astros to an 8-3 victory against the Boston Red Sox that snapped a four-game skid.

The game was 1-1 and Buchholz (0-2) had retired eight straight before walking Luis Valbuena with no outs in the fifth. George Springer singled with two outs before Buchholz plunked Carlos Correa to load the bases.

Rasmus then launched a 93 mph fastball with two strikes to the seats in right-center field for his fifth career grand slam and Houston’s second this season.

“It’s a really good pitch whenever you’re able to throw it where you want to, but the ball was moving a lot today,” Buchholz said. “For the most part, I felt like I did a pretty good job with executing the pitches I was throwing at times. Me and Colby faced each other a lot; he got me today.”

Rasmus drove in a fifth run with a double in Houston’s three-run eighth for his most RBI since he had six on June 2, 2011.

Buchholz yielded six hits and five runs, striking out six in 52/3 innings to remain winless in four starts this season. It’s his first career loss to the Astros in five starts, which included two complete games. He entered with a 1.38 ERA with 39 strikeouts against Houston.

Manager John Farrell praised his work despite the loss.

“I thought today he had excellent feel for his secondary pitches,” Farrell said. “He kept a very good fastball-hitting team off-stride for the most part, (except for) the grand slam. Granted, you’re going to look at the line score and it’s going to say five runs, but I thought the way he threw the ball today coming off the start against Toronto, he was making very good progress.”

Mike Fiers (2-1) allowed five hits and two runs with six strikeouts in 51/3 innings for his second straight win.

Mookie Betts hit a leadoff single and advanced to second on an error by Fiers on a pickoff attempt. Dustin Pedroia walked before the RBI single by David Ortiz made it 1-0.

Houston tied it in the second when Marwin Gonzalez scored on a groundout by Jason Castro.

Fiers settled down after the single by Ortiz, retiring 15 of the next 16 batters before a double by Pedroia to start the sixth.

A single by Travis Shaw with one out in the inning loaded the bases and chased Fiers.

“The last three or four games we’ve come out and we’ve been able to put up a crooked number on the board early,” Farrell said. “We’re creating a number of opportunities in games to get a little bit of a cushion. We were unable to cash in fully in that first inning today but still we’re having a lot of good at-bats.”

Fiers was replaced by Will Harris, and Brock Holt hit a sacrifice fly that scored Pedroia to cut the lead to 5-2. But Harris retired Chris Young to limit the damage.

The Red Sox added a run on a double by Josh Rutledge with two outs in the eighth.