Too many times this season, the Mets have watched as opportunity has slipped by.

Francisco Alvarez wasn’t going to let that happen again on Wednesday night.

With runners on first and second and no outs in the fourth inning, the Mets’ rookie catcher punched a full-count offering from White Sox starter Touki Toussaint through the right side of the infield, scoring Pete Alonso and sending Jeff McNeil to third.

Alvarez’s 103-mph RBI single helped set the tone for the Mets’ comfortable 5-1 victory. His hit pushed the Mets’ lead to 2-0 after fellow rookie Brett Baty had homered an inning earlier.

The Mets tacked on three more runs in the bottom of the fourth inning to take a 5-0 lead they did not relinquish behind Justin Verlander’s dominant eight-inning, one-run start.

For the 21-year-old Alvarez, who also singled in the eighth, it was another moment in a special rookie season.

“That’s what’s been fun, the home runs and all that stuff is real sexy, but those are things that are gonna allow you to maintain things,” manager Buck Showalter said of the composure Alvarez evinced with his single.

“Wanting to be emotional is part of this game, but to keep it corralled into the funnel of the competition.”

Alvarez, who has an .840 OPS and 19 homers this year, had already left his stamp on the Mets’ three-game series against the White Sox when he launched a pair of two-run homers on Tuesday night during an 11-10 victory.

But for Showalter, it’s the smaller moments — such as the walks Alvarez drew Tuesday — that make him confident in the rookie’s ascension to stardom.

“I said last night, the most impressive thing he did … was two walks,” Showalter said before the game Wednesday. “I got the home runs, not anybody can do that, that’s impressive, I got that but that’s when I go, ‘Okay, he’s starting to slow it down.’ ”

Not only is Alvarez contributing to the Mets’ success, but also he’s chasing history: his 19 homers are drawing ever nearer to the rookie catcher home run record, held by Johnny Bench, who hit 26 in 1969.

More impressive is that Alvarez has excelled at the plate while handling a full slate of catching duties, working with the Mets’ cast of pitchers that include future Hall-of-Famers like Verlander, whose gem Alvarez caught on Wednesday.

“He does his homework and [pitchers] see him in that room with them, and it’s important to him and it’s sincere, and I think he likes it,” Showalter said. “It’s not work. … It’s not selfishly for his benefit. It’s just because he’s chasing what he can do.”