Starting pitcher James Paxton limps off the field with the help of Manager Alex Cora, left, and a trainer in the first inning of the Red Sox’s 10-2 loss to the Astros on Sunday at Fenway Park in Boston. Michael Dwyer/Associated Press

BOSTON — Alex Bregman hit a three-run homer to key a five-run fifth inning, Yordan Alvarez followed with his third homer in two games and the Houston Astros beat the Boston Red Sox 10-2 on Sunday to complete a three-game series sweep.

It was the fifth straight win for the AL West-leading Astros, who also swept a three-game series in Fenway Park last season. Houston has won seven of its last eight series in Boston.

“Big swings, a ton of good at-bats throughout,” Astros Manager Joe Espada said of the series.

Jeremy Peña added a two-run homer and Yainer Diaz had a two-run double for the Astros, who improved to a season-best seven games over .500 (62-55).

Boston starter James Paxton limped off the field after straining his right calf while making a quick move to cover first on a grounder in the opening inning.

“I felt like I got kicked in the calf. Then, I kind of turned around, took another step and I felt it again,” Paxton said. “I was like: ‘It’s not good. It’s my calf.’ I felt it pop.”

The Red Sox have lost four straight, and they’ve given up a major-league worst 47 homers since the All-Star break. Boston came in an MLB-best 16-3 in Sunday games.

Boston first baseman Dominic Smith pitched a scoreless ninth, with his first pitch recorded at 32 mph. He tipped his cap walking off after getting a loud ovation.

Hunter Brown (10-7) struck out nine in 5 1/3 innings, allowing two runs.

With Houston leading 1-0, Bregman hit a shot against Brennan Bernardino an estimated 441 feet that left Fenway completely over the Green Monster. Alvarez then sent his drive into the center-field bleachers.

Alvarez went 2 for 2, increasing his average to .482 in 15 career games in Fenway with eight homers and 20 RBI.

“Just to be able to be his teammate and be able to watch what he does on a day-to-day basis is special,” Bregman said of Alvarez. “He hits for average line-to-line, hits the ball out of the ballpark anywhere, so he’s always fun to watch and he’s very clutch, too. … He always gets his ‘A’ swing off.”

Peña’s drive also cleared the Monster seats, coming in a four-run sixth that made it 10-0.

Reliever Lucas Sims (1-6) was the loser after Bernardino’s wild pitch allowed a runner that he left on to score

TRAINER’S ROOM

Astros: Espada said “everything was positive” on ace RHP Justin Verlander after he had a rehab start for Triple-A Sugar Land on Saturday night. They were waiting to hear from Verlander, but the plan is another rehab start before thinking about coming back to the majors. … Bregman slid into a wall hard chasing a foul pop, but stayed in.

Red Sox: 3B Rafael Devers had the day off. “He’s been grinding through it,” Red Sox Manager Alex Cora said. “It makes sense and hopefully (Monday) he’ll be back.” … SS Trevor Story is still expected to take BP on the field Monday as he works back from shoulder surgery quicker than originally expected.