NEW YORK -- By the early part of last decade, the idea was that the Mets, unlike just about every other team in baseball history, would be immune to starting pitching worries. Matt Harvey and Zack Wheeler had already reached the Majors. Jacob deGrom was soon to follow. Noah Syndergaard and Steven Matz arrived by 2015. The Mets’ trove was unrivaled.

That it didn’t work out quite the way the Mets envisioned was not entirely shocking, given the nature of starting pitching injuries. Harvey got hurt, twice. Wheeler, too, before leaving via free agency. A new front office made moves to guard against further erosion.

And yet no matter what the Mets did, their grand pitching dreams continued to unravel. On Monday, Matz allowed eight runs, including three homers, in a 16-4 loss to the Nationals at Citi Field, hours after the Mets learned that Marcus Stroman had elected not to play the rest of the season due to COVID-19 concerns. Matz now owns an 8.20 ERA. Rick Porcello, one of those offseason depth signings, has a 6.92 mark. Syndergaard and Michael Wacha are on the injured list. Wheeler is in Philadelphia.

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The Mets, for the first time in a long time, have a bona fide rotation problem.

“I’ve got to be better,” Matz said, focusing the issue on himself.

Coming off a strong second half of the 2019 season, Matz was supposed to be among the least of the Mets’ problems. Instead, he has become increasingly susceptible to home runs, allowing an MLB-high eight of them through 18 2/3 innings -- more than twice his career rate coming into the season. Homers by Asdrúbal Cabrera, Trea Turner and Juan Soto all hurt Matz on Monday, with Soto’s soaring 463 feet beyond the Home Run Apple in center field. By the ninth, things had grown so bad that the Mets called on utility infielder Luis Guillorme to pitch.

Of the 16 balls the Nationals put in play off Matz, 10 were hit at least 90 mph, with five reaching triple digits.

“I’m just trying to figure out -- what is it?” Matz said. “Why are they so on me these past two games? I saw some of the replays, and those pitches weren’t terrible pitches, but they’re hitting them out of the park. I’m just trying to figure all that stuff out.”

Whatever the reason, the result was a rotation ERA that rose to 5.34, which ranks near the bottom of the Major Leagues. Take two-time reigning National League Cy Young Award winner deGrom out of the equation, and that mark increases to 6.35.

The problem is not just how poorly Mets starters have performed, but how few options they have to correct their issues. Without Syndergaard, Stroman and Wacha, the Mets don’t even know who will start for them on Wednesday, let alone next week. Since becoming general manager less than two years ago, Brodie Van Wagenen has jettisoned much of the organization’s upper-level starting pitching depth -- Justin Dunn, Anthony Kay, Simeon Woods Richardson and Jordan Humphreys -- in trades.

Van Wagenen made a point to replace those pieces with veterans this past offseason, signing Porcello and Wacha to one-year deals, but those moves have yet to prove fruitful for the Mets.

Which brings them back to Matz, who entered this season as a pillar of the rotation. Finally healthy after years of arm trouble, Matz gave the Mets 30 starts in each of the past two seasons, setting career bests last year in innings and strikeouts. A significant reason why was his 3.52 ERA over his final 14 starts, portending -- at least, the way the Mets saw it -- better things to come in 2020.

Instead, Matz has struggled. Following Monday’s loss, both he and manager Luis Rojas hinted at the possibility that he could be tipping pitches. Matz will meet with pitching coach Jeremy Hefner, and possibly even some of his teammates, this week to discuss the issue.

If tipping is indeed Matz’s problem, the Mets need him to correct it, and fast, because at this point, they’re wed to him. Neither Stroman nor Syndergaard will return anytime soon. Few -- if any -- answers exist at the team’s alternate training site in Brooklyn, or outside the organization.

To become a successful rotation again, the Mets will need to improve from within.

“I’ve got to address some things, especially why I’ve been giving up the home run ball,” Matz said. “It’s been killing me so far. I think we have a great staff. I think our potential’s really high. And so for me, personally, I’m really disappointed in myself and letting the team down. I’m just going to get to work, and just try to be better.”