The span between victories seemed as if it had taken forever, from Sept. 19, 2014, to April 12, 2017. After two lost seasons following Tommy John surgery, Zack Wheeler was a winner again for the Mets. And he felt a lot better for it, exorcising any remaining doubts.

But that was the 26-year-old righthander’s only win among his first three starts. So on Sunday night at chilly Citi Field, he was chasing victory No. 2, against first-place Washington, under daunting circumstances.

The Mets have been ravaged by injuries and slow starts, leading to a lack of runs. And now the lineup had to deal with Max Scherzer.

So Wheeler needed to limit the damage. That didn’t go well right off the bat — Daniel Murphy’s bat, to be exact.

Wheeler’s old teammate hit a grand slam in the top of the first. Then Wheeler turned back into the guy making a strong comeback, putting on a brilliant one-hit shutout show in the next six innings.

He threw a season-high 101 pitches, allowed four hits and two walks and struck out six in the season-high seven-inning outing. But the Nationals still handed him a 6-3 loss, finishing off the three-game sweep.

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“I really hadn’t gone deep into a game yet, so to get seven and bear down after that first inning was a good feeling,” Wheeler said after dropping to 1-2. “But any time you get a loss, I should’ve done better.”

Still, he displayed a good changeup after tweaking his grip. All in all, those last six innings showed him something.

“I’ve had good times since I’ve been back here and there,” Wheeler said. “But today after that first inning, it sort of reassured me that that’s where I need to be and that’s where I can be . . . Especially against this team. That’s a confidence- booster. A good lineup.”

That lineup got to him quickly. Wheeler nicked the elbow guard of Adam Eaton with a fastball to start the game. Trea Turner followed with an infield single after the count went full.

Wheeler fired a 2-and-1 fastball to Bryce Harper. Single to left. Bases loaded, none out.

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“You could just see the command wasn’t there,” Terry Collins said.

Murphy unloaded the bases two pitches later, driving a two-seam fastball over the wall in right-center. “It caught a little too much plate,” catcher Kevin Plawecki said. “Moving past that inning, he just kept them off-balance and was able to locate everything and got ahead of hitters and made some pitches when he had to.”

Wheeler impressively won two rematches in the third, overpowering Harper with a 97-mph fastball and getting Murphy to go down swinging at a slider.

Wheeler had a lot of free time on his hands in 2015 and 2016. He put it to good use.

“I watched a lot of baseball in the two years that I was gone,” Wheeler said. “I learned a lot of things, watched a lot of guys pitch. The best guys go out there and go after guys. I told myself that when I got back, that’s what I was going to do.”