Boston’s Alex Verdugo goes airborne while heading home to score on a two-run double by J.D. Martinez in the sixth inning against the Kansas City Royals Tuesday night at Fenway Park. Charles Krupa/Associated Press

BOSTON — J.D. Martinez drove in four runs, including two on a go-ahead double in the sixth inning, and the Boston Red Sox outlasted the slumping Kansas City Royals 7-6 on Tuesday on a sweltering night at Fenway Park.

The Red Sox, who had four homers in each of their previous two games, won their fifth straight despite not going deep Tuesday. Boston pitchers allowed three homers by the Royals for the second straight game, but Kansas City’s skid continued with its seventh loss in a row.

Whit Merrifield led off the game with a homer for Kansas City off Nick Pivetta. Michael A. Taylor and Ryan O’Hearn each hit two-run shots for the Royals, who fell to 1-7 on a 10-game trip that concludes Thursday afternoon in Boston.

The clubs combined for 25 hits in the game, which stretched more than 3 1/2 hours in sweltering conditions that only eased slightly from a game-time temperature of 95 degrees.

Yacksel Rios (2-0) got the win with 1 2/3 scoreless innings of relief. Matt Barnes pitched a perfect ninth for his 18th save.

After Merrifield put the Royals up right away, the lead changed hands six more times before Martinez lined a double to right in the sixth with two runners on. Michael Chavis and Alex Verdugo scored easily and the 7-6 lead held.

Martinez also had an RBI single in the first and drove in a run on a sacrifice fly during Boston’s two-run fourth. Every Red Sox player in the starting lineup finished with at least one hit.

Royals starter Brad Keller faced one batter in the sixth before being replaced by Jake Brentz after Bobby Dalbec hit a leadoff single to left. Brentz (2-1) couldn’t hold the lead, walking Verdugo and putting two runners on for Martinez, whose double to right put Boston back up. Brentz allowed one run and one hit, walked one and struck out three.

Pivetta went 4 1/3 innings, allowing six runs and nine hits. He walked two and struck out five before being pulled after O’Hearn’s two-run homer put Kansas City back up 6-5.

NOTES: LHP Chris Sale, who is recovering from Tommy John surgery he had in 2020 and pitched to batters over the weekend, is scheduled to throw again Wednesday, Manager Alex Cora said. “The live BPs are great, but how he feels the next day is the most important thing and so far, in between that live BP and up to now, he’s feeling amazing,” Cora said. “He’ll go through his work tomorrow and we’ll see how he reacts on Thursday.”