NEW YORK -- Some hours before the Mets kicked off a three-game homestand, which in turn began a two-week soft stretch in their schedule, Mets chief operating officer Jeff Wilpon summoned general manager Brodie Van Wagenen and manager Mickey Callaway together for an atypical sort of meeting. Wilpon, a member of the team’s ownership group, wanted to brainstorm how the Mets could recover from their 17-20 start. He did not threaten Callaway’s job, according to a source, nor issue an ultimatum. The tone was nevertheless clear: the Mets must play better.

“This meeting had a different focus,” Callaway said. “This meeting was about, ‘How can we be better? How can we get going in the right direction?’ And it was very productive.”

Hours later at Citi Field, the Mets could not have rushed more immediately or impactfully to Callaway’s aid, enjoying their most productive first-inning rally in 30 years. The first eight batters to face Marlins starter Pablo Lopez all reached base, including Amed Rosario, who punctuated the rally with an opposite-field grand slam. All told, the Mets sent 13 men to the plate in the first inning, scoring eight times in what became an 11-2 blowout of the Marlins.

• Box score

It marked the first time since June 16, 1989, in Philadelphia that the Mets scored at least eight runs in the first, and the first time since July 12, 1979, that they achieved the feat at home.

It also came at a most opportune time for Callaway, who needs as many wins in as short a span as possible.

“None of us are satisfied with what’s been going on to this point,” the manager said.

Friday, that feeling changed almost immediately, when Jeff McNeil opened the bottom of the first with a hustle bunt single. Although McNeil’s ensuing baserunning blunder -- he was thrown out trying to go first-to-third on a J.D. Davis single -- could have been a rally-killer, the Mets made sure it wouldn’t matter. They plated their first run on a wild pitch, their second on a Wilson Ramos infield hit and their third on a Brandon Nimmo bases-loaded walk. Up next was Rosario, who blew the game open with his first career grand slam.

The Mets were not done. After Robinson Canó added an RBI single to cap the first-inning rally, Michael Conforto and McNeil added solo homers in the second and third, respectively. By game’s end, McNeil had set franchise records for hits, batting average and on-base percentage through 100 career games, offering Zack Wheeler -- who struck out 11 over seven innings -- cozy levels of support in the victory.

“Everything was clicking there,” McNeil said. “To get out to a good lead is something that’s been tough for us, so it is huge.”

It was huge for a Mets team wary of sliding too far down the NL East standings, just as it was enormous for Callaway -- a first-time manager hired under a previous front-office administration. The Mets have not replaced a manager midseason since 2008, when they dismissed Willie Randolph and installed Jerry Manuel as their interim manager.

That year, the Mets failed to live up to outsized preseason expectations. This year has proven similar, particularly given Van Wagenen’s January boast to his rivals: “Come get us.” Despite talent and health, the Mets struggled to back Van Wagenen’s words over the season’s first six weeks, falling 4 1/2 games back of the Phillies after a 1-5 road trip through Milwaukee and San Diego. Only toward the end of that week, Conforto said, did he feel the tenor of the clubhouse change.

“You can fall into a hole that it’s a long season, but that can be a trap sometimes,” Conforto said. “You get a little too complacent, and all of the sudden, you’re 10 games out and you have no shot. … All of the sudden, it can be June and July and August and the season is behind us.”

The Mets do not want to suffer that fate -- particularly not now, as they begin a stretch of 16 consecutive games against sub-.500 teams. Nor does Wilpon, who called Friday’s pregame powwow for just that reason. Given his Mets’ immediate response, Callaway joked that he called Wilpon afterward to suggest a similar meeting every day.

“It’ll be a good feeling tonight, going home,” Callaway said. “We’ve got to come back tomorrow and do the same thing, or that’s going to be meaningless. We understand that. And I’m not trying to rain on the parade, but it’s one game, just like one loss is one loss. We have to continue to focus, and come out every day and play like we did tonight.”