MILWAUKEE — Pete Alonso reminded us all once again how fickle baseball can be, how one swing can change a season, a team, a legacy and maybe even the path of someone’s entire career.

“Pete! Pete! Pete!” people shouted as Alonso walked through the spartan hallway in the bowels of American Family Field on his way to the post-game presser, a celebration in itself. Of course, these were all close friends and family waiting outside the victorious clubhouse. But they might as well have been everyday Mets fans, whose opinions and views on the lanky but collapsing Met have surely focused on one pitch, one swing and one point in time.

“It’s a very special moment,” Alonso said afterwards in his usual subdued manner.

Actually, it’s most likely a life-changing moment.

Let’s face it: No owner, no matter how wealthy, is dishing out $158 million (which is what they offered last year, according to Joel Sherman), or more, for a star who took the virtual power collar in September and October. . Oh, Alonso produced hits here and there, he played generally airtight defense (despite one dropping a foul pop-up late) and he dutifully reported to work every day, confused or not, just as he did during his entire 162-game regular season record.

Oh, club owner Steve Cohen and his financial people (yes, even self-made billionaires have advisors) would have made Alonso some sort of perfunctory offer if the Mets had gone into the wild-card round with nothing but whining from Alonso. But there would have been no excitement, no momentum and really no chance for Alonso to be back in a Mets uniform.

He seemed to go, go, go.

Now, after his wild-card winning home run in the last inning, the Mets and Alonso have something fun to talk about. The season was already a success, but his mighty hitting turned these never-say-die Mets into the biggest, happiest story in sports. When they snuck into the playoffs, thanks to a pair of cardiac comebacks in Game 161 and the first paper tiebreaker in baseball history (sorry D-Backs), they qualified as a wonderful local story.

Alonso took his Mets team nationally when he hit star Brewers closer Devin Williams’ 3-on-1 changeup over the right field wall, making the Mets the belle of this October ball and truly changing everything. Francisco Lindor’s home run off the Braves’ Pierce Johnson that made it all possible was perhaps the greatest home run in Mets history.

Now, three days later, Alonso even surpassed his old teammate Lindor, the do-it-all Met, who is their clear and obvious MVP. Alonso was supposed to be the second man, but he wasn’t even that this year. Oh, his numbers look good. He hit 34 home runs. He somehow posted a 123 OPS-plus, the exact same mark as last year.

But it all felt very empty. He never seemed to get any big hits. It was always the kid Mark Vientos or the underrated, underpaid veteran Jose Iglesias, or of course Lindor. Until the home run that left Brewers fans crying into their Miller beers, Alonso’s top five hits all came in the first half, based on the added win probability.

That all changed when Williams attempted a switch on the outside half with Lindor and Brandon Nimmo on base. Alonso’s eyes undoubtedly widened.

“Just one of those terrible games for Williams,” said one scout. “His best pitch is the changeup. Alonso crushes changes.”

Well, he crushed this one just enough to turn a 2-0 deficit in the ninth inning into a 3-2 lead, which immediately caused a stir in the sold-out stadium. Sadness permeated the park for the small team that is always the regular season champion but almost never gets it done in October.

(My theory: Milwaukee’s front office is smart enough to find enough bargains to dominate the little things that work above 162, but big and highly paid stars often win the day the playoffs arrive.)

As for Pete, the slump is right there on his baseball reference page: no home runs since September 19, not even an extra base hit.

The slump became so pronounced that every time he came to bat, we would say to each other in the press box, ‘Pete has got to come.’

And now that he’s done what we were all waiting for, it’s all in the past. He was due, and he did it in style with his legendary swing that changed everything for the better.

Alonso doesn’t really acknowledge or address his failures. (Maybe he thinks it’s bad luck?) But anyone could reasonably assume that this super talent was urgent.

“Hopefully this will allow him to exhale and relax a bit, and he can burst into tears,” a Met said afterwards, saying what’s on everyone’s mind.

A lot of good things have happened for the Mets this year. Vientos became a real power source. David Peterson, who salvaged the biggest Mets win in nine years, is a pitching star. If Pete is Pete again, who knows? They’ve already come a lot further than almost anyone thought, but if Pete is Pete, who knows how far they can go?