NEW YORK -- As he batted in the eighth inning of an otherwise unremarkable loss to the White Sox last Thursday, Pete Alonso’s batting average sat at .201. In the midst of the deepest slump of his career, Alonso managed to poke a single into right field, saying afterward that he considered it a harbinger of better days to come. Even if only he believed it, Alonso felt he was thawing.

It has taken him only a matter of days to make believers of everyone else. In the four games since that seemingly innocuous single, Alonso has collected three singles, two doubles, a triple and the pair of home runs he hit Tuesday in a 9-3 win over the Yankees in the Bronx. He has given the Mets more production over his last four games than he did in the three weeks that preceded them.

“He’s a ridiculous player,” hitting coach Jeremy Barnes said. “If we swing at the right pitches and do the right things, the ball’s going to hit the barrel at some point.”

Alonso had already singled home a run when he returned to the plate in the third inning Tuesday, crushing a three-run homer over the left-field fence for his first long ball since July 6. Three innings later, he hit a far longer solo shot 431 feet to center, the first of back-to-back homers with Daniel Vogelbach. In that fashion, Alonso became the first Mets player since José Reyes 13 years ago to produce a multihomer game at Yankee Stadium. His eight career home runs against the Yankees are tied for second most in franchise history behind David Wright’s nine.

“I’m just really happy that today was an excellent day,” Alonso said.

Alonso’s outburst provided plenty of support for Justin Verlander, who faced little resistance from an Aaron Judge-less Yankees lineup over six innings. The Mets’ bullpen proved shakier, requiring David Robertson to be called on to escape a bases-loaded jam in the eighth. With that, Verlander improved to 3-1 with a 1.46 ERA over his last six starts, and 1-0 with a 0.75 mark in two career Subway Series games.

But on this night, the lion’s share of credit went to the Mets’ 2-3-4 hitters -- Francisco Lindor, Jeff McNeil and Alonso -- who finished a combined 8-for-13 with two doubles, two homers, six runs scored, two stolen bases, two walks and eight RBIs.

Unlike Lindor and McNeil, Alonso began the season hot, straddling a 60-homer pace for much of April and May. It wasn’t until the second third of the schedule that Alonso began scuffling -- still popping homers from time to time but offering little else as his batting average fell 40 points from late May to late July. The slump began with some hard contact that found its way into gloves. As it deepened, Alonso began shedding a few of his better habits, particularly regarding pitch selection. At his nadir in mid-July, he went 1-for-31.

To recover, Alonso dove deep into scouting reports, cage work and on-field batting practice, correcting what Barnes referred to as “milliseconds and little bitty things.” He studied past video of himself and tried to mold his swing back to that shape. By the time he poked his single into right field against the White Sox, Alonso felt he was close to where he wanted to be. He was just waiting on the results to prove it.

“I think it always drives him to never take anything for granted or assume anything,” manager Buck Showalter said. “That’s why he’s such a good player.”

Within the context of the Subway Series, Alonso helped deliver a memorable win in front of a sold-out crowd in the Bronx, which the Mets were happy to have. Whether it triggers the type of sustained success that will be necessary to avoid a Trade Deadline selloff remains to be seen. The Mets are still six games under .500 and won’t be able to break even prior to the Deadline.

But as baseball players, coaches and executives are fond of saying, process matters more than results. For the Mets, the type of process that might carry them to the postseason begins with hitters like Alonso, who can carry the team when they’re going right.

“Sometimes, this game’s really hard and you just kind of lose it for a little bit,” Barnes said.

Alonso took a longer view, saying his multihomer game “doesn’t prove anything” if he can’t back it up with continued success.

“Today was my day,” Alonso said. “Tomorrow, I just want to win as many pitches as possible and be early, be relaxed and be on time.”