Though they've gotten this homestand off to a perfect start, the Washington Nationals still have some work to do on Labor Day.

The preseason NL East favorites begin a possible make-or-break three-game series Monday with the division's current front-runners, the New York Mets.

New York (71-65) caught the Nationals in the standings with a momentum-shifting home sweep July 31-Aug. 2 and has since taken off, with that series and several aggressive moves at the trade deadline sparking a 23-11 run that's opened up a four-game lead on its chief rival.

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The sweep began a dismal 4-13 stretch for Washington (71-65), but the club has recovered with wins in 13 of its last 19 and enters the series on a five-game win streak following a four-game home sweep of downtrodden Atlanta.

"Certainly it's tightening up," Mets manager Terry Collins said after his team's 4-3 loss to Miami Sunday.

Washington battered the Braves' pitching for 36 runs in the series and hit seven homers, including three in Sunday's 8-4 victory.

Bryce Harper has homered in three straight and is batting .421 over his last 18 games. Ryan Zimmerman is hitting .439 with six homers and 18 RBIs over a 10-game streak.

"I've been saying all along at some point we're going to make a run. Hopefully this is it," outfielder Jayson Werth said. "We've got our (top) guys going."

The resurgent offense will attempt to help out struggling Max Scherzer (11-11, 2.89), something it failed to do in the staff ace's two prior season meetings with New York.

Scherzer yielded one earned run over 14 2-3 innings in those starts but lost both after receiving only one run of support. He hasn't won at all in six consecutive outings and is 0-3 with a 6.14 ERA in his past four.

The All-Star surrendered 11 hits in six innings Wednesday but held St. Louis to two runs in a 4-3 Washington win.

Scherzer's winless drought has gone on even longer at Nationals Park. Since no-hitting Pittsburgh June 20, he's 0-3 with a 5.16 ERA in five home starts and allowed four runs or more in three of those outings.

The Mets, who dropped two of three in Miami to narrow the gap, send out a slumping pitcher of their own in Jon Niese (8-10, 4.17). The left-hander has permitted 18 runs and 23 hits over a three-start stretch and was reached for six in five innings of Tuesday's 14-8 loss to Philadelphia.

Niese also has lost four straight starts against Washington and is winless in five since tossing 7 1-3 scoreless innings at Nationals Park on Aug. 18, 2012.

The Mets have won each of Niese's last five road starts even though he's allowed 12 runs over 11 1-3 innings in his past two.

New York scored 23 runs in those games and will field a considerably different lineup than Scherzer faced May 1. David Wright and Travis d'Arnaud have returned from injuries and the offense has gotten a needed power boost from Yoenis Cespedes' acquisition and rookie Michael Conforto's promotion.

Cespedes homered for the fourth time in five games Sunday and is 10 for 23 during that span. D'Arnaud is batting .415 with three homers and 15 RBIs over his last 12.

The Mets are 7-6 against Washington in 2015 and have split six games at Nationals Park. The teams conclude the season with three at Citi Field beginning Oct. 2.