Updated

Armed with a losing record for the first time in over a month, the Washington Nationals hope to get on track Tuesday evening whey they begin a three-game series with the New York Mets.

The Nationals have lost four of five and 10 of their last 15 games to fall under .500 (28-29) for the first time since they were 13-14 back on April 30. That came as a result of a loss to the Atlanta Braves, the same scenario that led to this current dip under the even mark.

Washington finished up a three-game set with Atlanta by dropping Sunday's 6-3 contest, held to just five hits for a second game in a row. Ian Desmond had two of those in the finale, including a home run.

Nathan Karns took the loss after giving up four runs -- three earned -- on seven hits in 4 2/3 innings of work.

"I'm continuing to grow up here," said Karns, who was making his second career start. "I'm able to become what is more my game up here. It's just nice that I am making progress but I'm still not satisfied."

The Nationals have been satisfied with most of Jordan Zimmermann's starts this season, though the right-hander will try to rebound on Tuesday from his worst outing of the campaign.

Taking aim at a ninth victory, Zimmermann instead suffered a 9-6 loss at Baltimore last Wednesday as he allowed season highs of seven runs, 10 hits and three home runs over six-plus innings. He fell to 8-3 on the season with a 2.37 earned run average.

The 27-year-old also suffered an earlier loss this season to the Mets despite yielding just two runs over five innings of work. Zimmermann fell to 3-3 lifetime in 12 starts against New York with a 3.05 ERA.

The Mets are also looking for answers after losing all three of their games this past weekend to the NL East's last-place club, the Miami Marlins. That came after New York had swept the rival New York Yankees in a four-game home- and-home series that gave the Mets five straight victories overall.

The Mets were bested 11-6 in Sunday's finale as young star Matt Harvey was roughed up for four earned runs over a season-low five innings. He did not get a decision as the bullpen failed to protect a two-run lead after five innings.

Lucas Duda, Ike Davis and Omar Quintanilla all homered for the Mets.

"This one was tough to take," said Mets manager Terry Collins. "Certainly there was a lot of things unexpected today. We'll just go into the day off, regroup and come back out. The fact that maybe a couple of guys are breaking out, maybe we'll be better offensively."

That would be preferred by starter Jeremy Hefner, who is coming off his first victory of 2013.

The righty went 0-5 with a 4.76 ERA through his first 10 starts -- all Mets losses -- before beating the Yankees on Wednesday. Hefner yielded three runs over six innings, working around nine hits without a walk. His season ERA fell slightly to 4.74 following his first win since Oct. 3 of last year.

Hefner did not factor into the decision of his outing versus Washington on April 20, allowing three runs over four innings. The 27-year-old yielded a solo homer to Desmond in the second inning and a two-run shot to Bryce Harper in the third.

Hefner had lost each of his previous three career starts versus the Mets and has a 5.57 ERA over the four meetings.

He won't have to face Harper, who is on the disabled list due to a left knee injury, but fellow Washington outfielder Jayon Werth is on track to return to action tonight. Werth has not played since April 29 due to a strained right hamstring.

Werth hit .556 during a six-game rehab stint with Class-A Potomac and is batting .260 this season with the Nationals over 27 games.

The Mets won two of three in New York over the Nationals from April 19-21 after Washington won 14 of the 18 meetings a season ago.