#J.A. Happ shuts down Red Sox as Yankees’ win streak reaches 10

BOSTON — The Yankees appear set to storm into the postseason and J.A. Happ is making a case to be a key part of it.

As the Yankees won their season-high 10th straight on Saturday night, the left-hander dominated the Red Sox in an 8-0 victory, tossing eight scoreless innings.

And in extending their longest winning streak since 2012, the Yankees also reduced their magic number to reach the postseason to one, having moved into the four seed in the American League.

Happ got plenty of support from the lineup, especially from Clint Frazier, who drove in three runs.

The 37-year-old Happ continued his turnaround, from rotation afterthought to a certainty to pitch in the playoffs. He’s now 2-1 with a 1.93 ERA in his past six starts, the lowest mark by a Yankees starter in that span.

It’s quite a contrast from where the left-hander was earlier in the season, when he strongly implied the Yankees were skipping his starts to avoid next year’s $17 million vesting option from kicking in.

Now, it’s hard to believe the Yankees would be in their current position without Happ.

Of what the improvement has meant to him, Happ said, “I don’t think I can put it into words. I appreciate the support of the players here in this room. It certainly means a lot.”

Aaron Boone sang Happ’s praises and added the left-hander is “obviously gonna be on the team” in the postseason, but his role is to be determined.

“I think [he’ll be] playing a big role, but we’ll cross that bridge in the next week to 10 days,’’ said Boone, adding that he was impressed by the fortitude Happ has shown during a difficult season.

“Really impressive,’’ Boone said. “This season, early on, I think he showed me a level of mental toughness, of professionalism, of focus that’s been really admirable. He’s been one of the stories of us moving toward a successful season and one of the anchors in the rotation.”

He was terrific again against a feeble Red Sox team that is just playing out the string in an ugly season. Happ gave up just four hits — and no walks — while striking out nine.

By the time Happ even took the mound, the Yankees led 2-0.

The Yankees added two more runs in the fourth, as the Red Sox were done in by some bad defense — mostly from Xander Bogaerts, who made a pair of errors in the inning.

Luke Voit added an RBI single in the top of the fifth and Frazier belted a homer to right-center to make it 7-0 later in the inning.

Meanwhile, Happ made it look easy in a 113-pitch outing.

He gave up just an infield hit to Bogaerts in the first and a single to center by J.D. Martinez in the fourth before Kevin Plawecki’s double with two outs in the seventh. And he pitched out of a jam in the eighth, when the Red Sox had runners on the corners and no one out and didn’t score.

The Yankees will look to close out the series sweep Sunday at Fenway Park, looking to put some distance between themselves and the Twins for the fourth seed in the American League — as well as keep pressure on the Rays for the lead in the AL East. They remain 3 ½ games behind Tampa Bay with eight games left.

Saturday’s win was also the Yankees’ 12th in a row over Boston, matching the franchise record for consecutive victories over their archrivals, last accomplished in 1952-53.

Happ said the Yankees learned of the record following Saturday’s win and were “excited to get out there” Sunday and break it.

“It’s a little fluky,’’ Boone said. “They haven’t been quite the same team. Look, it’s always fun beating those guys. We respect who they are and they’re all great games. Enjoy it while it lasts.”