Mets starting pitcher Steven Matz delivers against the Washington Nationals...

Mets starting pitcher Steven Matz delivers against the Washington Nationals during the seventh inning at Citi Field on Sunday. Credit: Kathleen Malone-Van Dyke

Steven Matz threw his first pitch on Sunday afternoon and Adam Eaton lashed it inside the third-base bag for a single. Matz shook his head and walked behind the mound with a disgusted look.

One pitch in.

“It’s just, the first innings I feel like have been where I’ve been faltering,” Matz explained. “When I saw that — jammed him and he peppered it down the line — I was like, ‘Son of a gun.’ I just wanted to get ahead of him.”

Matz’s first-inning ERA coming in was 9.53. The last time he faced the Nationals, on July 31, he gave up seven runs in two-thirds of an inning as the Mets lost, 25-4, in the game in which Jose Reyes made his unfortunate pitching debut. So you can understand if Matz’s initial-inning woes were on his mind.

This time he got out of the inning unscathed, striking out super-rookie Juan Soto with two men on for the final out. Matz went on to allow one run in seven innings in the Mets’ 15-0 loss at Citi Field.

Yes, the final score was 15-0. When Matz left it was 1-0, and even though the bullpen gave up a ridiculous 14 runs in the final two innings — the regular relievers, not Reyes — the larger takeaway was Matz’s impressive performance. He gave up five hits, walked one and struck out seven.

“Matz was great,” manager Mickey Callaway said. “I think that given where he’s been lately, it was a big step for him. He looked like the guy that we saw earlier in the season — throwing the ball over the plate, getting in a rhythm, shaking things off, doing a good job focusing on the next pitch — and he threw a great game for us.”

Matz fell to 5-11 as his ERA improved to 4.36. Cy Young Award candidate Jacob deGrom has reminded us all that pitcher win-loss records can be misleading. But even though Matz was a hard-luck loser Sunday, he has earned his overall record with inconsistent pitching over 24 outings.

Matz is 27, three years removed from pitching in the World Series as a rookie and having a sandwich named after him at an East Setauket deli (quite filling, I’m told; haven’t had the pleasure).

Matz’s career record is 20-26. He has had trouble staying healthy. As the Mets look to an uncertain future with a new general manager taking over after the season, Matz needs to take a big leap forward like Zack Wheeler if he is ever to fulfill his once-boundless promise.

On Saturday, Wheeler shut out the Nationals for seven innings and earned high praise from Callaway, the same skipper who shipped the former phenom to Triple-A to start the season with an unsubtle “put up, shut up and grow up’’ message. Callaway said he now considers Wheeler as much of a sure thing as deGrom and Noah Syndergaard.

“I hope this is who he is. I think he could be this,” Callaway said of Wheeler. “He’s in that category now where you wake up in the morning [and say] we have Wheeler now. We’re going to have a good game.”

Matz still has the stuff to get to that level. A lefty who throws 93-mph sinkers, which he still was doing in the seventh on Sunday, should be better than 20-26.

The message from Callaway to Matz is different from the one to Wheeler. Matz has an admitted tendency to lose focus when something goes wrong — such as the leadoff hitter slashing your first pitch for a single.

“The biggest thing is I need to stay calm and in the moment,” Matz said. “That’s something that’s definitely beneath the surface.”

He did, and the Mets got to see the best of Long Island’s favorite lefty. Now they need to see it about six or seven more times before the season ends to be confident in what they have going into 2019.

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