WASHINGTON -- The window for action came and went, easily lost Wednesdayin the commotion of a frantic eighth inning, one in which the Nationals seized a 4-3 victory from the Mets.

Yet it was all manager Terry Collins could think about, just moments after the Mets let slip away what would have been a critical series victory against the team they're chasing in the standings.

"That's my fault,'' said Collins, who blamed himself for not intervening as reliever Bobby Parnell let a 3-1 lead become a 4-3 deficit.

See alsoBoxscore: Nats 4, Mets 3

As the calamity unfolded, closer Jeurys Familia was warming up. But he had not been given enough time to bail out Parnell, who languished despite his excellence since returning from Tommy John surgery.

Against Parnell, Michael Taylor's two-run single tied it and Danny Espinosa's double pushed the first-place Nationals ahead.

"Just poor timing for a bad day on my part,'' said Parnell, who brought an 0.73 ERA into the game. "These guys did everything they were supposed to. I just didn't do my part. That's totally on me.''

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Of course, just as in Collins' case, that wasn't entirely true, either. There was room for blame for other Mets.

The slumping Lucas Duda came up small in a pair of two-out situations, stranding four runners and missing a chance to change the complexion of the game.

Noah Syndergaard held the Nationals to only one run, but he labored so badly while making 98 pitches that he was pulled after the fifth, having issued five walks and allowing five hits.

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Yet through all of that, the Mets took a 3-1 lead into the eighth thanks to a clutch two-run double by Kirk Nieuwenhuis and a run-scoring single by Kevin Plawecki in the fourth.

It wasn't enough.

"It's definitely tough, and in the heat of the moment, you get emotional,'' Nieuwenhuis said. "But 162 is 162, and if you overemphasize this series, you lose track of tomorrow.''

The Mets needed only for Parnell to withstand the eighth before turning the reins over to Familia, who has emerged as one of the NL's finest closers. But trouble arose too quickly for the Mets to react.

In the span of about 40 seconds, Ian Desmond worked a one-out walk and Matt den Dekker lined the first pitch he saw into centerfield.

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Right then, Familia sprang into action in the pen. On the mound, Dan Warthen stalled for time. The pitching coach's words seemed to do some good, at least for a moment. Pinch hitter Tyler Moore roped a smash at leftfielder Nieuwenhuis. Now, only one out separated Parnell from an escape.

It was in this moment -- and in this moment alone -- that Collins could have bought more time to bring in Familia. But even then, Familia had been warming up for little more than three minutes.

And until den Dekker's hit, there was little reason for Collins to get Familia up in the bullpen. Yet Collins absorbed all the blame, despite his lack of wiggle room.

"That's all on me, that's not on Bobby,'' he said.

Parnell stayed in the game, with the potential tying run still not in scoring position. But that changed with a critical wild pitch.

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Needing only one strike to finish off Taylor, Parnell buried a 2-and-2 curveball in the dirt. Plawecki blocked a similar pitch earlier in the inning, but this one clanked off the heel of his mitt and trickled away.

Now, the tying run stood on second base.

Taylor ripped Parnell's full-count fastball to left. Espinosa followed with the game-winner.

With the Nationals playing at far from full strength, and with the series on the line, Collins called the game "a huge loss.''

"Yeah, we let this one get away,'' Collins said. "There's no one to blame but me.''