MLB

Relief pitchers doom Mets, Young

The Mets are quickly finding out that when you shop for bargains, there’s usually a reason they’re on sale.

They got a taste of that yesterday as their shoddy bullpen struggled again, surrendering six runs in a 7-3, 11-inning loss to the Nationals at Citi Field — wasting a superb effort from starter Chris Young.

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“It’s been inconsistent,” GM Sandy Alderson said of the bullpen following the loss. “That’s probably as positive an adjective as I could use.”

It was consistently bad yesterday.

D.J. Carrasco gave up a pair of runs in the eighth to blow a 3-1 lead, and then Blaine Boyer, after an easy 10th, collapsed and surrendered four runs an inning later.

“You’ve gotta convince them they gotta get beat making someone swing the bat,” manager Terry Collins said after the Mets turned what looked to be a solid victory into an ugly defeat very quickly.

“This is the big leagues. You’ve gotta plant some pitches, and we’re walking guys at too high a rate.”

Carrasco walked one, Taylor Buchholz three.

The first culprit was Carrasco, who replaced Young to start the eighth. He immediately gave up a double to Ivan Rodriguez that right fielder Lucas Duda couldn’t catch up to.

“It’s on me,” said Duda, who was optioned to Triple-A Buffalo after the game, though not because of that play.

“I took a bad route and got beat. I take full responsibility. It kind of cost us the game. It changed the momentum and was a terrible play.”

Carrasco made things worse by walking pinch-hitter Matt Stairs. Washington soon tied the game with a bloop single by Ian Desmond and an RBI groundout by Rick Ankiel.

“When you throw the game away, it’s very frustrating,” Carrasco said. “[The walks] are very unacceptable. We have to attack the strike zone, we have to be aggressive, and for the most part, we haven’t done the job.”

That included Boyer, who was designated for assignment after the loss following an RBI single by Ivan Rodriguez that gave the Nationals the lead and then a three-run homer by Laynce Nix that put the game away.

“That’s the ultimate right there,” Boyer said before learning of his fate. “You can’t even put it into words. It’s an utter letdown. I’m disgusted with myself.”

If the Mets hope to stay competitive, they’ll need to get better production from plenty of areas, but especially the pen — which is why they called up Jason Isringhausen and Ryota Igarashi after the game.

“The only advice I can tell them is that I know sometimes games are tough to swallow,” said Francisco Rodriguez, who was called upon to retire one batter in the ninth. “You’ve gotta put it behind them, and that’s not easy to do. I have faith in my boys, though.”

But the Mets’ pitchers were hardly the only culprits yesterday, since their hitters struck out 17 times, and have whiffed 27 times the last two days. They also didn’t get any extra base-hits yesterday.

And even after Washington tied the game, the Mets had their chances. Jose Reyes started the 10th with a single to center, but Willie Harris couldn’t get a bunt down and struck out. Even after Reyes advanced to third from first on a David Wright groundout, the Mets failed to score.

So a day after Rodriguez and Carlos Beltran gave Mets fans a reason to be optimistic, the bullpen gave them another dose of reality.

dan.martin@nypost.com