As Pete Alonso rounded the bases Tuesday night, he kept his head down and his facial expression subdued. His teammates in the Mets dugout didn’t outwardly celebrate. The fans behind home plate at Citi Field, though, gave away the game.

“Pete! Pete! Pete!” they chanted as Alonso touched home, the Mets vise-gripping another win. Four innings later, as he caught Luis Guillorme’s throw to first to bookend a double play and he let out a fist pump — emotion finally breaking through — the Mets had that victory in hand, their fifth in a row, their 12th in 13 games. And, for the second-straight night, Alonso was at the heart of it.

His first time up, Alonso took a change-up from Hector Noesi, thinking it was inside, and umpire Dan Iassogna called a strike. His second at-bat, Alonso swung and missed at a similar pitch. When Noesi went to it again in the fifth, Alonso hit a laser shot into the left-field seats that Curtis Granderson barely gave the courtesy of a chase, insuring the Mets’ lead in an eventual 5-0 win over the Marlins on Tuesday night.

“I recognized it,” Alonso said. “Trusted myself and got my hands there and made really good contact and it went for me.”

In an alternate world, in which things had gone according to conventional wisdom for the Mets, Alonso might be one of the few bright lights left in their season.

The first baseman, who made the All-Star team and seems the clubhouse leader for NL Rookie of the Year, would be cast as the center of the Mets’ future. After Tuesday’s game, he had a slash line of .259/.364/.584, and had hit his 36th home run, just five behind the franchise’s single-season record. Even if the stakes had been lower, like most of baseball expected for an early August series between the Mets and the Marlins, that would be something worth smiling about for the organization.

But, as things stand for the Mets, who suddenly find themselves in the thick of things, the stakes are anything but low. And in large part, that’s thanks to Alonso, who has broken out of a slump with two home runs in two nights.

“When I was kind of going through a tough time, it’s like I would get pitches that I was looking for, and I’d foul them back or swing and miss or just not put it in play hard,” Alonso said. “That’s the main thing. I feel like I’ve been chasing less and I’ve been doing a better job of commanding the strike zone.”

Mickey Callaway concurred.

“He’s staying on the ball a little bit better,” the manager said, while noting that Alonso’s tendency to chase pitches still flashes at times.

Alonso’s contribution Tuesday night, and the Mets’ victory itself, was far less dramatic than Monday’s come-from-behind thriller. The Mets took an early lead and, with Alonso’s help, built it to an insurmountable point.

He’s still the center of the franchise’s future, and with the Mets suddenly in the midst of a playoff race, he’s the center of its present, too. On Tuesday, though, against the league’s bottom-feeders, it all just felt routine. Just as it should.