Pete Alonso hit a walk-off home run in the seventh inning Thursday afternoon as the host New York Mets completed a doubleheader and series sweep of the Washington Nationals with a 5-4 win.

The Mets won the opener 4-1 and carried a 4-1 lead into the seventh inning of the second game before the Nationals tied it against Trevor May and Jeurys Familia.

But Alonso, who was hitless in 29 plate appearances entering Tuesday's series opener, hit a one-out, sky-high fly to left off Kyle Finnegan (4-4) that just cleared the fence and the grasp of Andrew Stevenson. Alonso finished 3-for-4 in the second game and was 6-for-12 in the series.

The Mets never trailed Thursday in either half of the doubleheader. The sweep was a timely one for New York, which entered the series with seven losses in eight games but moved within a half-game of the first-place Philadelphia Phillies by virtue of Thursday's wins.

Mets spot starter Trevor Williams and the Nationals' Erick Fedde traded zeroes in the second game until New York broke the tie in the fourth. Michael Conforto led off the inning with a double and trotted home when J.D. Davis doubled on the next pitch. Davis moved to third on a single by Jonathan Villar and scored as James McCann beat out the back end of a potential double-play ball.

The Nationals chased Williams in the fifth when Adrian Sanchez doubled with one out and Tres Barrera followed with a single. Seth Lugo entered and surrendered a sacrifice fly to Yadiel Hernandez before getting Victor Robles to hit into a fielder's choice.

Villar capped a 3-for-3 game with a two-run homer in the sixth.

The Nationals rallied in the top of the seventh, when they loaded the bases against May via two singles and a walk. Familia (6-2) retired Robles on a pop-up but uncorked a wild pitch, which allowed Luis Garcia to score. He then gave up a two-run single that skipped under the glove of second baseman Jeff McNeil.

Williams, in his Mets debut, allowed one run on three hits and two walks while striking out two in 4 1/3 innings. Fedde allowed two runs on six hits and one walk while striking out four over four innings.

--Field Level Media