NEW YORK — Roman Anthony, the Red Sox’ stoic wunderkind, let loose for one fleeting moment Thursday night.
His two-run, second-deck home run off Yerry De los Santos in the ninth inning was the highlight of a 6-3 win over the Yankees. As the ball soared to right field, Anthony watched it go, threw his bat away, and unfastened his batting glove before beginning the trot around the bases.
For an almost always unemotional rookie, it was a rare bit of fun-loving flair. Manager Alex Cora noted that it was the first time in Anthony’s 59 games that Anthony felt moved enough by the juice of the occasion to go through with a bat flip.
“It just happened,” Anthony said, seemingly back to being his shy on-camera self after the game. “I don’t even know. I don’t usually do that. It just happened.”
A player’s first game at Yankee Stadium can have that effect.
The long ball served as the exclamation point on his standout Bronx debut: 2 for 5, three RBIs, two runs, and a walk.
In his accelerated introduction to playoff-race baseball — an environment in which Anthony has surpassed about every expectation — it was another test aced.
“A huge moment for us,” said Alex Bregman, who went 3 for 5 with a double and a walk. “To be honest, he’s probably the most mature 21-year-old, baseball-wise, I’ve ever been around in my life. I’m trying to find out what he does wrong, honestly. We don’t know if he has any vices or anything. He just does everything the right way.”
Lucas Giolito said: “It’s incredible. There’s not much else to say. Looking at him, it’s like, wow, there’s 21-year-olds that can come up and do it at the highest possible level. Yeah, we’re very lucky to have him.”
And Cora: “He wants to be the best out there. Today we needed everything from him.”
Anthony’s blast allowed the Sox to breathe at the end of a weird night at the plate. They repeatedly failed to turn the game into a blowout, stranding a mind-boggling 14 runners and finishing 3 for 19 with men in scoring position.
The Yankees were 2 for 7 in those spots, leaving 10 on.
“We got the line moving, which is good,” Cora said. “Now we got to score.”
Nathaniel Lowe also had a big game, contributing two RBIs, including a go-ahead double in the seventh.
The Red Sox (69-59) are 6-1 against the Yankees (69-58) this year. One more win would clinch the season series, which would be the playoff-seeding tiebreaker if the clubs finish with the same record.
With something resembling an old-school Red Sox-Yankees pace, the game took 3 hours, 25 minutes, the Sox’ longest nine-inning contest of the year.
Neither team recorded a 1-2-3 inning until Garrett Whitlock retired the side in the bottom of the eighth, surviving a scare in the form of Anthony Volpe’s fly ball to deep right field.
Oh, and these teams will meet up again the next three days.
“It felt like back in the day,” Cora said. “It feels like every game is going to be a grind.”
In what quickly turned into a back-and-forth affair, Giolito (4⅔ innings, three runs) and Yankees righty Luis Gil (five innings, two runs) engaged in a duel of mediocrity.
Giolito walked three and allowed five hits. Gil, similarly, walked five and gave up four hits.
“My personal outing left a lot to be desired,” Giolito said. “But we won, and that’s all that matters right now. Winning games, especially against teams like this.”
The Sox struck first, but only because the Yankees committed three errors in the second inning, gifting them several bases and a run. The last, a bad throw by catcher Ben Rice on David Hamilton’s steal of second, allowed Ceddanne Rafaela to scoot home from third.
Rice, a Cohasset native, made up for it with a solo home run in the bottom of the second.
That made it 1-1. The teams also were tied at 2-2 and 3-3. The Yankees nearly made it 4-4 in the seventh, but Steven Matz worked around Rice’s one-out triple by retiring Jazz Chisholm Jr. and Paul Goldschmidt.
“It really doesn’t matter how it looks,” Cora said. “We just got to get 27 [outs].”
That set the stage for Anthony’s latest big moment. Bregman, heaping praise on his Fenway Park home clubhouse locker neighbor, cited Anthony’s ability to compartmentalize as one of his strengths.
In the seventh, Anthony struck out swinging against funky lefthander Tim Hill, leaving the bases loaded. Instead of trying to make up for it in his next opportunity, however, Anthony treated that at-bat as its own episode — and made the most of it.
“The moment is never too big for him,” Bregman said. “He knows who he is. He knows what he does well.”
As Anthony rounded the bases, much of the announced crowd of 47,036 streamed for the exits. He described the overall atmosphere as “probably what I imagined, and maybe even a little more.”
And the heckling from fans in right field?
“A lot more than what I expected,” he said with a smile. “It’s a fun atmosphere. I like playing here.”
Tim Healey can be reached at timothy.healey@globe.com. Follow him @timbhealey.