Mets centerfielder Austin Jackson dives to catch a line drive...

Mets centerfielder Austin Jackson dives to catch a line drive by the Phillies' Odubel Herrera during the third inning Monday night in Philadelphia. Credit: AP/Matt Slocum

PHILADELPHIA — The 2018 Mets’ postseason chances are officially zero.

They beat the Phillies, 9-4, Monday night, but the Cardinals’ win against the Braves mathematically eliminated the Mets (70-80) from playoff contention.

A season that started with what seemed like genuine October aspirations is ending with a dozen games good for little but pride and personal stat-padding.

“We should’ve played better,” manager Mickey Callaway said. “I don’t have any excuses for those type things. We could’ve played better, and we didn’t.”

What went wrong? Plenty. The Mets’ realistic shot at the postseason was over months ago. After their hot two weeks to open the year, they encountered what assistant general manager John Ricco called “a little bit of a perfect storm”: poor play all around, injuries to some veterans and struggles for some young players — all while a rookie manager with a new coaching staff tried to find their way and general manager Sandy Alderson stepped away because of cancer. The Mets went 15-39 in May (10-18) and June (5-21).

“That was pretty much the season,” Ricco said.

Said Callaway: “For me, June happened. It didn’t not happen. We have to do everything we can to make sure that a June doesn’t happen again. Because it derails your whole season. It’s unfortunate, but that is what happened, and it did derail our season.”

Ricco and Callaway see improvement — and hope — in this mildly successful second half. The Mets are 31-25, tied with the Braves for best in the NL East. There will be lots for the new GM and the rest of the brain trust to decide over the winter — Should they keep the rotation together? What to do at center, second and catcher? — but Callaway specifically has been pleased with the growth of the Mets’ starting pitchers and the recent offensive diversity. With the likes of Amed Rosario, Jeff McNeil and Michael Conforto having strong summers at the top of the lineup, the September Mets aren’t nearly as homer-reliant and offensively limited as the May Mets.

Monday’s win offered a glimpse of that. Conforto went 3-for-5 with a career-high six RBIs, including a go-ahead RBI double with two outs in the seventh and a three-run homer in the ninth. He raised his career-high RBI total to 75. McNeil also had three hits.

“This is the Michael Conforto that everybody wants to see,” Callaway said. “This is one of the better players in the league when he’s going like this.”

Zack Wheeler (12-7, 3.31 ERA) allowed four runs — all in the fifth — in seven innings. Philadelphia broke through on J.P. Crawford’s three-run triple into the rightfield corner. Callaway said the Mets will discuss shutting Wheeler down due to workload concerns.

The second half has been a positive one for Wheeler (1.68 ERA, at least seven innings in nine of 11 starts), as it has been for the Mets.

“The bright side is seeing how Mickey and the team righted the ship in the second half and have played really competitively for a long period of time, and not just in September but against some teams that are fighting for playoff spots,” Ricco said. “I have to fold that into the takeaway on the season, which is this team, there are some strengths to build on, a lot of what we’ve seen recently.”

Notes & quotes: Former Phillies manager Charlie Manuel gave David Wright, who is wrapping up his playing career this month, an “NYM” card from the Citizens Bank Park out-of-town scoreboard, which pairs nicely with the No. 5 off Boston’s Green Monster from Dustin Pedroia … The Mets tweaked their rotation to keep Noah Syndergaard, who will pitch Wednesday, on regular rest, which also allows him to make one extra start, the season finale Sept. 30. Jason Vargas will pitch Thursday in Washington … Left behind by the Mets, who will have Syracuse as their Triple-A affiliate starting next year, the Las Vegas 51s hooked up with the A's on a two-year player-development contract. … Devin Mesoraco (neck) has been swinging in the batting cage and said he expects to play again “in a couple of days.”