CHICAGO -- Over the first two months of this season, the Mets featured an average offense. Ordinary. Pedestrian.

They certainly were not bad, as coaches and team officials tended to point out. But they were not the type of good one might expect from a lineup featuring Francisco Lindor, Pete Alonso, Brandon Nimmo and J.D. Martinez up top. From Opening Day through May 30, the Mets ranked 20th in runs per game, 22nd in OPS and 14th in wRC+, a metric designed to measure overall offensive output.

What exactly happened to change things isn’t entirely clear. The players-only meeting the Mets held during the final week of May might have played a role. Hotter temperatures, especially at home at Citi Field, couldn’t have hurt. But the reality is that no one thing transformed the Mets from average to elite.

The Mets don’t much care how they arrived at this point, only that they did. After hammering National League Rookie of the Year frontrunner Shota Imanaga for a career-high 10 earned runs in an 11-1 throttling of the Cubs on Friday afternoon at Wrigley Field, New York improved to 12-3 over its last 15 games. The team features MLB’s best record over that stretch, in large part because its offense has also been the best.

Once again dating to May 31, the Mets rank first in MLB by a wide margin with 6.6 runs per game, while also leading the league in OPS and wRC+.

“We know we have a good lineup,” Martinez said. “I feel like we kind of preach it, and sometimes it shows up, and sometimes it doesn’t. But that’s just baseball.”

They padded those totals Friday against a pitcher who had established himself as one of the league’s feel-good stories in the first-half -- a 30-year-old Japanese rookie with a lightweight fastball and an outsized personality. The Mets jumped all over the former on a hot summer day at Wrigley, most notably on homers from Martinez, Nimmo and Francisco Alvarez. For the first time in franchise history, their first two batters reached base safely in each of the first four innings. Jose Iglesias, meanwhile, finished 4-for-5 with three RBIs.

New York’s success included a four-run rally in the fourth, with three of the runs charged to Imanaga, who did not record an out that inning. His ERA climbed more than a full earned run, from 1.89 to 2.96.

But while Imanaga’s breakdown was news in Chicago, the Mets considered it a routine matter of business. Over the past three weeks, they’ve manhandled opposing pitchers more often than not, generating extended rallies and a run of offense that has been clearly, obviously, overwhelmingly better than average.

“We’re in a really good place,” Iglesias said.

Asked to define a single reason for the Mets’ recent success, co-hitting coach Jeremy Barnes pointed to nothing more than improved luck, as evidenced by their vastly improved batting average on balls in play (the team has a .332 mark since May 31, compared to .274 from Opening Day through May 30). Repeatedly, Barnes said the Mets have “doubled down, tripled down” on really being convicted in their plan.

Since their team meeting on May 29, Mets hitters have taken a different process in their daily meetings, going around the room each day to speak aloud their plan for the upcoming game. It could be laying off a particular pitcher’s splitter, for instance, or jumping on early pitches in a count.

Friday, their scheme was to attack Imanaga’s fastball, which they did with unprecedented success.

“The offense was amazing,” said Mets starter Jose Quintana, “especially against that lefty, one of the best in baseball.”

Now, the Mets’ charge will be to maintain this type of output not just against the Cubs this weekend, not just for the rest of June, but for the rest of the season. Given the talent on this roster, they believe they can do it.

After all, they’ve done it for three weeks running. What’s another three months?

“One through nine, everybody’s clicking,” manager Carlos Mendoza said. “We can do damage. We get guys on, we’re getting big hits. Our approach with runners on base continues to get better. So yeah, I think it’s a combination of a lot of things. But it comes down to having good hitters right now that are executing their approaches.”