A lot of firsts in the second game of the season as the Mets make quick work of the Cardinals with a 6-2 victory behind an effective debut by Jacob deGrom.

DeGrom gave up New York’s first walk, Todd Frazier was charged with the team’s first error, and Anthony Swarzak left the mound holding his left oblique, to be christened Mickey Callaway’s earliest injured player. Other than that, it was a fine day at Citi Field.

With his long locks a thing of the past, deGrom had his back door slider dancing for 5 2/3 innings allowing an earned run on four hits, accompanied by seven strikeouts and a walk.

Like Syndergaard before him, the right-hander got offense from the usual suspects and some pleasant surprises from platooning players.

Todd Frazier doubled in a pair to start the festivities in the first, adding an additional RBI on a sac fly in the bottom of the eighth. In the fourth, Travis d’Arnaud delivered a letter-high fastball into the center field seats, while an inning later, Yoenis Cespedes golfed a breaking ball souvenir to left.

“Nothing better than getting off to a good start,” d’Arnaud said. “The clubhouse feel in here is amazing and we’re all having a lot of fun.’’

Ex-Dodger Adrian Gonzalez pulled a 3-1 high-heater for a base hit to right, only to be gunned down at third trying to advance on Juan Lagares’ shallow lofted single to center. Lagares, who’s been left at the outfield alter, banged another base hit up the middle in the eighth for a 2-4 day.

Robert Gsellman in place of deGrom, brought his rediscovered sinker into the sixth, fanning the hot-hitting Jose Martinez, for his fourth strikeout in a row. After allowing back-to-back singles to Yadier Molina and Paul Delong, Gsellman was bailed out by Swarzak who got Greg Garcia looking at a fastball and Dexter Fowler on a pop up to center.

In his second day in the Mets manager’s seat, Mickey Callaway mixed up his line up swapping Frazier from the five spot to the four spot and moving Asdrubal Cabrera from cleanup to leadoff. The converted pitching coach also spread the wealth by playing Lagares in lieu of the prolific Brandon Nimmo and gave Wilmer Flores a taste of first base, in which he delivered a flare up the middle that three converging Cardinals could not contain.

Jeurys Familia closed out the show with a four-out outing consisting of a couple of strikeouts and a bevy of balls in the dirt for his first save.

“It was a big win on Opening Day,” deGrom said. “I wanted to come out here and win again today, start the season out 2-0 and hand the ball over to Matz and let’s see what he can do Sunday.’