BOSTON — After meandering through most of September, the Yankees’ season has reached a make-or-break point. Over the final week and a half of the regular season, they have six games scheduled against two of the teams — the Boston Red Sox and Toronto Blue Jays — they are fighting with for the final two postseason spots in the American League.

And through their first two of those games in Boston, the Yankees have acquitted themselves well — and they have slugger Giancarlo Stanton to thank for that.

In Friday’s 8-3 victory over the Red Sox, Stanton led the Yankees with three hits and four runs batted in. A day later, Stanton did it again, guiding the Yankees to a 5-3 win, their fifth in a row, and into a tie with the Red Sox for A.L.’s top wild-card spot.

With the Yankees (88-67) trailing by one run with two outs in the eighth inning, Stanton delivered arguably the biggest swing of his tenure in pinstripes, sending the first pitch he saw from Red Sox reliever Darwinzon Hernandez over the Green Monster in left field and out of Fenway Park for a go-ahead grand slam.

“A great feeling,” an understated Stanton said afterward. “A lot of emotions going on. Just glad I was able to do that, just compress everything and be on time for the fastball and something good happened.”

His teammates, though, were more effusive about the blast that was estimated at 452 feet but felt longer. As Stanton jogged around the bases, his teammates threw their arms into the air and bounced with glee. The many Yankees fans at Fenway Park cheered.

“It was incredible,” said starter Nestor Cortes, who allowed two runs over four and a third innings on Saturday, and has produced a 2.85 earned run average for the Yankees this season. “The whole dugout was electric. We were so happy. As soon as he rounded second base, he looked at us and we gave him like a flex. It was a great feeling.”

Since the start of August, Stanton has been the Yankees’ best hitter — Saturday’s blast was his 17th in that span. Stanton attributed his surge to making his swing more direct to the ball, in order to make more contact, and lifting the ball more into the air, after a stretch of too many hard-hit ground balls.

This season — and not just the past two months — has been a strong reminder of Stanton’s powerful bat. After playing in a combined 41 games over the previous two seasons because of a litany of injuries, Stanton has been the Yankees’ second most productive batter, behind star outfielder Aaron Judge.

Including Saturday, Stanton is hitting .275 with 33 home runs and 91 R.B.I. with an .872 on-base plus slugging percentage this season. He has played in 132 of the Yankees’ 155 games.

“We put a premium on trying to keep him healthy and what’s the best way to do that,” Yankees Manager Aaron Boone said. “But I think that he’s tweaked and altered some things along the way, both off-season and in season, to allow him to stay healthy. He’s done a great job preserving himself physically and making sure he’s able to post as much as he has this year.”

Stanton came to the rescue on Saturday thanks to Yankees’ pitching that held Boston’s powerful offense mostly in check. Luis Severino, making his second appearance since the 2019 postseason because of Tommy John surgery and ensuing setbacks, earned the win while striking out four over two scoreless innings.

Sitting in the dugout in between his innings, Severino said he talked to catcher Gary Sanchez about what he wanted to throw when he took the mound again when trailing by a run. But after the Yankees loaded the bases for Stanton with quality at-bats — Brett Gardner and Judge walked, and Anthony Rizzo was hit by a pitch — Severino said he changed the plan because he told Sanchez that Stanton was going to send a ball over the fence for the lead.

“That’s not the first time he’s been in a big situation and came through,” said Severino, who is normally a starter but is being eased back into the big leagues as a reliever. “I could feel it.”

After Red Sox Manager Alex Cora brought in left-handed reliever Hernandez to face Rizzo, Stanton said he thought to himself, “They better get him out.” That was Stanton’s confidence speaking, and over the past two months he has certainly backed it up.

“I’m looking forward to watching it back on replay a few times tonight,” Boone said of Stanton’s blast home run. “In this atmosphere, in this environment, just to take the air out of the building, that’s up there for me in the ones I’ve seen G hit.”