Mets' Adrian Gonzalez, right, celebrates his three-run homer with Todd...

Mets' Adrian Gonzalez, right, celebrates his three-run homer with Todd Frazier, left, as San Diego Padres catcher A.J. Ellis looks on during the seventh inning of a baseball game against the San Diego Padres in San Diego, Sunday, April 29, 2018. Credit: AP / Kyusung Gong

SAN DIEGO — In their last game of the season’s first full month, the Mets offered a glimpse of what they hope is to come with a 14-2 win over the Padres on Sunday.

Zack Wheeler, who opened the season in the minors, made his case as perhaps the team’s third-best starter behind Jacob deGrom and Noah Syndergaard. He tossed five innings of two-run ball, striking out nine.

First baseman Adrian Gonzalez, facing the prospect of decreased playing time as the Mets think about playing Jay Bruce at first occasionally, contributed his biggest game as a Met. He went 3-for-6 with a home run, a double and five RBIs.

And as the bullpen locked it down with four shutout innings, the batters blew it open late to set season highs in runs, hits (19) and steals (four). Nine Mets position players — every starter plus Brandon Nimmo — had at least two hits, a first in franchise history.

The Mets finished April — they’re off Monday before a homestand against the Braves and Rockies — at 17-9 and lead the NL East by 1 ½ games. They won 15 games in April, the third-highest total in team history.

“The life from our players and the way they’re playing the game, I couldn’t have asked for more this first month,” manager Mickey Callaway said.

The Mets — who went 4-5 on the road trip — put the pressure on San Diego with runs early and often, including one in the first (Bruce’s RBI single), one in the second (Tomas Nido’s RBI single) and two in the third (Gonzalez’s two-run double). Five-spots in the seventh and eighth — highlighted by homers by Gonzalez, Todd Frazier and Jose Reyes — against the rebuilding Padres bullpen turned it into a laugher.

Yoenis Cespedes (2-for-2) had a double and two steals before exiting in the third with a sore left thumb. He said he expects to miss three days.

“There have been a couple of players that have started slow, including myself, but that’s why we’re a team,” Cespedes said through an interpreter. “There are some other ones who are playing really good and help us have the record we have so far.”

Gonzalez’s big game came two days after he and Callaway said that, despite lackluster traditional stats, more modern measures of success suggest he has been hitting the ball well and that better results will come. In one game, Gonzalez’s OPS went from .612 to .706.

“That’s why we were talking about those numbers, because they do matter,” Callaway said. “In the long run, things always even themselves out. That’s one of those games that’s going to start to even things out for the way he’s performing.”

Said Gonzalez: “Even a couple of my outs were hard hits . . . What matters to me is the guys in the front office are seeing the fact that I’m hitting the ball well. Really, at the end of the day, they’re the only ones that matter.”

The bullpen, without Jeurys Familia and Seth Lugo for the day, turned in four scoreless innings. Matt Harvey pitched the ninth, his first scoreless relief outing in three tries.

Wheeler bounced back from a 30-pitch, two-walk first inning, scattering six hits, including a two-run single by Freddy Galvis in the third. He didn’t walk another batter. Through four starts, he has a 4.09 ERA and 1.32 WHIP.

A significant part of Wheeler’s success Sunday was what he said was a new grip on his changeup, shown to him by pitching coach Dave Eiland between starts. It’s more of a split-changeup than a traditional one and it moves a lot more, turning it into more of a strikeout pitch than a weak-contact pitch.

“I still don’t know what I call it,” Wheeler said. “Me and Dave have been working on a little split, split-fastball, split-change . . . It was working in the bullpen the other day, so I just carried it into the game.”