WASHINGTON — Jeff McNeil fired his bat to the ground in disgust after hitting a grounder back to the pitcher in the second inning.

With that out, McNeil extended his career-longest hitless streak to 15 at-bats, but that would be the end of the drought: He blasted a Joe Ross fastball for a two-run homer in the fourth inning as part of a Mets outburst in which they took a 7-0 lead Monday.

“[McNeil] got the biggest hit of the game — that two-run homer to make it 4-0, extend that lead out so we can relax, put more pressure on their pitcher and then score more,” manager Mickey Callaway said after the Mets beat the Nationals 7-3.

McNeil’s homer was his 17th of the season. It was also his 12th homer on the first pitch of an at-bat. His 24 extra-base hits on the first pitch lead the major leagues.

Through June, McNeil had only six homers, but a change in approach has helped bolster his power numbers.

“He and [hitting coach] Chili Davis have really been working on getting a little taller and leveraging the ball a little bit more,” Callaway said. “You’ll notice his stance is a little higher — so that probably has something to do with the power numbers going up. He feels like he’s comfortable in that position and the kid can hit, so it’s nice to see the homers too.”

McNeil’s average has dropped to .322, quieting some of the talk about his NL batting title chances. Anthony Rendon began the day with the lead, at .337.

The falloff for McNeil has occurred since his return from the injured list after missing 10 days with a strained left hamstring. Even with the homer, McNeil is 6-for-31 (.194) since returning from the IL. Still, the homer might have been needed for his sanity.

“I think he was running out of bats,” J.D. Davis said. “He was slamming his bat too many times when he got out, so I think it was a matter of time before he found a good one.”

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