BOSTON — Cam Schlittler played with fire for four innings and got away with it. 

But then in the fifth, his defense added some lighter fluid and his start went up in flames. 

After Amed Rosario let a smoked ground ball go through his legs instead of turning a potential inning-ending double play, the first of four unearned runs came in on Schlittler that lifted the Red Sox to a 6-3 win over the Yankees on Thursday night at a sold-out Fenway Park. 

Former Yankees prospect Caleb Durbin delivered the deciding blow before the fifth inning was over, taking Schlittler deep for a two-run shot just over the Green Monster to break a 2-2 tie. 

The Yankees tried to mount a comeback in the ninth against their former closer, Aroldis Chapman, who loaded the bases with two outs before finally shutting the door. 

It was a sloppy loss for the Yankees (48-32), who committed four errors — making all six of the runs their pitchers allowed the unearned variety — and wasted some chances to cash in offensively before the scuffling Red Sox (33-46) came alive. 

Schlittler, who struck out nine across five innings, stranded a pair of runners in each of the first, second and fourth innings. He might have been able to do it again in the fifth, until Rosario’s fielding error opened the floodgates. 

The Yankees led 2-0 entering the inning before Schlittler issued a leadoff walk to Masataka Yoshida and then gave up a single to Ceddanne Rafaela. He followed that up by striking out Wilyer Abreu on a 100 mph sinker for the second time of the night. 

But Willson Contreras came up next and drilled a 112.8 mph ground ball to third base, where Rosario got his glove down but not far enough as the ball zoomed right underneath it, scoring Yoshida to make it 2-1. 

Jarren Duran then lifted a sacrifice fly to medium-depth left field, as José Caballero’s throw home was up the first base line, allowing the Red Sox to tie the game. 

The hot-hitting Durbin, whom the Yankees sent to the Brewers in the Devin Williams trade (before the Red Sox acquired him this February), capped off the rally by crushing Schlittler’s cutter into the Monster seats for the 4-2 lead. 

The Yankees later made it a one-run game in the seventh when Paul Goldschmidt, on the 12th pitch of a battle with former Yankees reliever Greg Weissert, hit a chopper to third that allowed Jazz Chisholm Jr. to score from third. 

But the Red Sox brought in lefty Danny Coulombe to face Ben Rice, who could not deliver the big swing in his hometown, instead grounding out to end the rally. 

The Red Sox then added a pair of insurance runs in the ninth after Yerry de los Santos bobbled a sacrifice bunt and Anthony Volpe threw wide on the second half of a potential inning-ending double play. 

The night had started better for the Yankees, as Goldschmidt continued to mash lefties and led off the game with a double off the Monster against Red Sox southpaw Connelly Early. One out later, Rosario singled and then with two outs, Jasson Domínguez delivered another hit from the right side, this one a single to score Goldschmidt for the 1-0 lead. 

Caballero later added his eighth home run of the year, drilling a fly ball just over the Monster off Early to put the Yankees ahead 2-0 in the fourth inning. 

Along the way, Schlittler escaped trouble that he partly created for himself. After a walk and a catcher’s interference in the first inning, he sailed a pickoff throw into center field, but then left runners on second and third. 

In the second, he let a weak pop-up fall between him and Austin Wells, and then hit a batter, but stranded them both. 

And then in the fourth, he gave up a single and double, but got out of it unscathed with a pair of strikeouts on a 99 mph fastball and 100 mph sinker.