Old MLB axiom: Don't believe what you see in April.

Meaning, of course, that fast starts by previously downtrodden teams are often fool's gold. Most times they merely precede June swoons.

Or May meltdowns.

The New York Mets, after getting off to a team-record best start, are right now happily challenging the veracity of that time-honored postulate.

After finishing 70-92 in 2017, the Mets shocked the baseball world with their rip-roaring beginning to the new campaign.

The boys from Flushing won nine of their first 10 ballgames and by mid-April had compiled a 12-2 mark.

Prior to a skid to open May, they had topped the National League East standings from day one this season.

Despite their recent slump, the Mets (18-15 through Monday) remain in the thick of the divisional race.

Their sensational start surpassed the club's previous best open to a season — an 11-3 mark racked up by both the 1986 and 2015 clubs.

Remember, if you will, that in '86 the Mets won their last World Series title. And in 2015 they reached the World Series where they lost to Kansas City in five games.

Thus, their fans and players alike are understandably, if prematurely, excited about a potential return to the Fall Classic.

Says star Mets slugger Yoenis Cespedes: "This team for me, is way better than the team we had in 2015. I think we're ready to go."

It is a ballclub that was sensibly constructed.

Last offseason, the Mets were loaded with vets who were possibly in a state of decline and depriving promising youngsters in their organization of a chance to move in and fully showcase their wares.

The Queens quandary was this: Should the Mets blow up their roster and start anew with the kiddie korps? Or try to squeeze one last hurrah out of the not-quite-washed up vets?

Wisely, as it turns out, the front office decided to do a little bit of both.

"I think we have a really good squad with young guys incorporated with the vets," new third sacker Todd Frazier told MAS.

"I think the biggest thing is we understand our roles, each guy — hitters and pitchers alike."

Frazier's role is to fill the void at the hot corner created when team leader David Wright never could come back from what now look like career-ending injuries.

A former Cincinnati Red, Chicago White Sox and New York Yankee, Frazier has brought with him his noted plate power and steady leather afield.

Todd is tied for second among Mets in both homers (five) and RBIs (21).

Almost as importantly, the affable Frazier — described as the most popular guy in every clubhouse he's been in — provides a stabilizing presence off the field.

(After our interview, Frazier responded to a MAS thank you by extending a fist for the bumping and an accompanying "You got it, big guy.")

In addition to Frazier, other grizzled vet contributors include Asdrubal Cabrera (team-leading .320 batting average) and first sacker Adrian Gonzalez, who has 17 ribbies.

They blend nicely with youngsters like speedy Amed Rosario, a speedy, slick-fielding shortstop with a slashing stroke at the dish.

And outfielder Brandon Nimmo, a high average hitter, who wore out Triple -A minor league pitching (consecutive .300 plus seasons) before finally getting a shot to exhibit his sweet lefty swing in The Show.

MAS asked Nimmo if he ever became frustrated, thinking his chance might never come.

"Not really," said Brandon. "I just tried to control what I could control.

"So, for me, it was about the effort I put out every day and the work I put in," Nimmo explained.

"I've just been trying to keep it as simple as that."

While much can be said for the vet and youngster mix, the biggest reason for the Mets strong start is probably due to the good health — at long last — of their formerly much-hyped starting pitching rotation.

Once considered the best collection of young arms in MLB, they have had trouble staying healthy the last two seasons.

In 2017, only Jacob deGrom made it through the season unscathed. The other four struggled with injuries.

This season, though, Noah Syndergaard, Steven Matz and Zach Wheeler have all avoided extended stints on the disabled list and have been respectable, if not spectacular.

But it is deGrom who has emerged as the staff's most consistent hurler over the past two seasons.

Jacob currently qualifies as staff ace with a 3-0 win-loss mark and a 1.87 ERA.

This, after 15-10, 3.53 numbers last season.

As twisted fate would have it, though, deGrom hyperextended his pitching elbow last week — by, of all things, swinging a bat in a game.

Jacob was just placed on the 10-day DL. He should be fine, though.

Before his freak injury, MAS asked deGrom if had shared any secrets for a healthy pitching wing with his oft-injured mound mates that may have enabled them to stay relatively healthy this campaign.

"Not really," replied deGrom. "Everybody's got their own routines. So, you just kind of stick with what works. I've just been fortunate to make every start the last two years.

"I do a lot of precautionary stuff that works — like varying my bullpen work between two or three days (after a start)."

For all their pitching potential, though, Frazier feels the best thing about the current construction of this Mets ballclub is that no one part of it has to carry an undue load.

"Hitters have to hit and pitchers have to pitch. It can't be pitching doing it one day and the hitters doing it another," offered Frazier.

"There's a fine line we have to cross and come together. And we've been doing that."

Thus far, it's been a topsy-turvy season in the NL East.

Atlanta and Philadelphia, divisional doormats the last few seasons, are currently battling with the third-place Mets for the divisional lead.

Meanwhile, defending champ Washington sputtered early and was under .500 for the first six weeks before recently reaching level.

So, with the New York club's mixing of age groups and meshing of plate work and pitching, another Mets' Miracle is NOT out of the question.

Diamond dictums be damned.

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