PITTSBURGH -- The Mets arrived here feeling good about their lineup. Before beginning a seven-game road swing, they had enjoyed a home run binge during a two-game pit stop at Citi Field, and they hoped the outbursts might be a sign of things to come.

"You think you're out of it," manager Terry Collins said. "You think you're swinging good. And then it comes back."

In this case, "it" was the team's persistent inability to hit when it counts, a maddening habit that again was in evidence Sunday in a punchless 5-2 loss to the Pirates.

The Mets dropped three of four against the Pirates, and scored just 11 runs in the series.

On Sunday, they had 13 hits and still found a way to scratch out only two runs, both in the ninth inning, after the Pirates opened a comfortable lead.

Chris Young's RBI groundout and Ruben Tejada's RBI single got the Mets on the board, forcing the Pirates to summon closer Mark Melancon.

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Daniel Murphy singled to put runners at the corners with two outs, bringing Curtis Granderson to the plate as the potential tying run. But Granderson flied out to rightfield to end it.

The rally came far too late for the Mets to cover up an afternoon's worth of failings.

"We just didn't get those key hits," said Travis d'Arnaud, who hit into a double play to kill a potential rally in the sixth.

Pedro Alvarez knocked in three runs against a shaky Bartolo Colon (8-6) with an RBI double in the first and a two-run homer in the fourth.

Ike Davis had a two-run single in the first, his first hit against his former team.

Colon stumbled through his worst outing in six weeks, allowing five runs and seven hits in six innings. It was the first time he had allowed more than two earned runs in a start since the Yankees roughed him up for six runs May 12.

In his previous seven outings, Colon was 6-0 with a 1.58 ERA, holding hitters to a .192 average.

"I was surprised as anybody," said Collins, who called Colon's early struggles Sunday "very shocking."

It quickly became clear that Colon wasn't fooling the Pirates, who scored three times in the first.

Even their outs were loud.

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"I just think that because I've already gone against them once, they've probably prepared, so they knew what I was coming with," Colon said through a translator. "They just had the time to prepare."

The bigger issues came at the plate, where the Mets stranded 11 and were 2-for-15 with runners in scoring position. Though winning pitcher Edinson Volquez (6-6) constantly found himself on the ropes -- scattering eight hits in his six innings -- he struck out seven and kept the Mets off the board.

The Mets had runners on base in each of the first seven innings. In five of them, they moved a runner into scoring position but came away with nothing.

Murphy had three hits and Tejada, Eric Young Jr., Lucas Duda and Eric Campbell each had two for the Mets.

They begin a three-game series in Atlanta Monday night facing what could be a critical point in the season.

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For all of their struggles to hit in the clutch, the Mets (37-45) are seven games behind the first-place Braves, who are coming off a four-game sweep of the Phillies. The Mets have lost four of their last five, and a Braves sweep would hand them a double-digit deficit for the first time this season.