WASHINGTON (AP) -- In the first half of the season, the New York Mets were one of the most surprising teams in baseball, entering the All-Star break with a 46-40 record.

The second half has been something completely different.

After their 5-2 loss to the Washington Nationals on Sunday, the Mets are just 11-24 in the second half.

Their only hope for improvement is 13 straight games against other struggling National League teams, Colorado, Houston, Philadelphia and Miami.

"We're not exactly playing great right now," New York manager Terry Collins said.

"You've got to get key hits. We sat here the entire first half and talked about the key hits we're getting with two outs. (Now) we're not getting them. That's a big difference."

On Sunday following a rain delay of nearly 2 1/2 hours, Bryce Harper had a home run and a triple, and Danny Espinosa homered to lift the Nationals.

Gio Gonzalez (16-6) pitched into the sixth inning, allowing one run and seven hits, and the Nationals won for the third time in their past four games.

Washington (75-46) has the best record in the majors and a five-game lead in the National League East over the Atlanta Braves, who lost 5-0 to the Dodgers on Sunday. The Nationals host the Braves in a three-game series starting Monday.

Tyler Clippard pitched a perfect ninth for his 27th save in 31 chances.

Jeremy Hefner (2-5) gave up five runs and eight hits as the Mets lost for the ninth time in 13 games.

Michael Morse led off the second inning with a single. With one out, Espinosa hit his 14th home run into the left-field visitors' bullpen to give the Nationals a 2-0 lead.

Washington got another pair of runs with three straight hits an inning later. Jayson Werth led off with a single, Harper followed with a run-scoring triple and scored on Ryan Zimmerman's single.

"Sometimes you get away with mistakes, and sometimes you don't, and today, I didn't get away with any," Hefner said.

"They're a good team. Don't get me wrong, but I made some mistakes and they capitalized."

It was Harper's team-leading sixth triple, and the 19-year-old added another run when he led off the fifth with his 12th homer off the front of the upper deck in right-center field, giving Washington a 5-0 lead.

Gonzalez wasn't particularly efficient, throwing 110 pitches in 5 2-3 innings, but he kept the Mets off the scoreboard until the sixth, when Ike Davis led off with a double and scored on Jason Bay's groundout.

New York had other scoring opportunities but didn't capitalize. Ronny Cedeno led off the fourth inning with a triple but was left stranded at third.

In the seventh, the Mets had runners on first and third with one out before reliever Craig Stammen got Scott Hairston to ground into a double play to get out of the jam.

New York added another run in the eighth inning off reliever Michael Gonzalez. Cedeno doubled with one out, moved to third on a groundout and scored on Kelly Shoppach's single.

The Mets were 1 for 11 with runners in scoring position.

"It's part of a pattern. We had a lot of guys on. We had plenty of opportunities, but just couldn't get a big hit when we needed it. We hung in there and made it a game. That was the good part," Collins said.