WASHINGTON — The Washington Nationals traded right-handed reliever Luis Ayala to the Mets today for a player to be named, a move designed to provide depth to New York's struggling bullpen.

The player going to the Nationals is expected to be minor league infielder Anderson Hernandez, who has not yet cleared waivers.

"I'm surprised. It's a little bit late for a trade," Ayala said. "But for me, I passed my best times in this organization."

The 30-year-old Ayala was the longest-tenured Nationals player, having joined the franchise when it was located in Montreal in 2003. After being reliable for the first four years of his career, going 26-24 with a 2.82 ERA in 258 appearances, Ayala had dipped to a 1-8 record and 5.77 ERA in 62 outings this season.

"Sometimes guys just have off years. I think that happens. It's a part of the game. ... He's certainly healthy, and I think a change of scenery will help him," Nationals general manager Jim Bowden said. "I think going to a pennant race will help him.

"I can't say enough good things about Luis. He took the ball for us anytime he was asked and did a phenomenal job his entire career. He'll be missed."

The Mets claimed Ayala — tied with Chicago's Carlos Marmol for the seventh-most appearances in the National League this season — off waivers and the teams worked out a deal. NL East-leading New York began Sunday with a two-game edge over Philadelphia.

"They're fighting for first place, so I'm going to do my best to clear my mind and try to help the bullpen," Ayala said.

Ayala pitched two scoreless innings against the Mets on Wednesday during New York's 12-0 road victory over Washington.

"The two innings he faced us, he threw strikes," Mets manager Jerry Manuel said Sunday in Pittsburgh. "He attacked the hitters. I kind of expect the same thing. Plus, he's experienced. That's important."

Ayala is expected to join the Mets for the finale of a four-game series in Pittsburgh on Monday. A roster move was expected to be made after Sunday's game.

"He had requested to be traded this year throughout the year," Bowden said. "We attempted to do so by the trade deadline and just were not able to make a deal that made sense for us. With a month and a half left before free agency ... we felt we needed to get something for him."

The Mets hope the acquisition of Ayala will help fortify a bullpen that's been in disarray since before closer Billy Wagner went on the disabled list earlier this month with a left forearm strain. Wagner had experienced shoulder problems for two weeks before being sidelined.

Wagner was expected to be activated from the DL on Monday, but discomfort in his left elbow Saturday changed those plans. The All-Star left-hander was to be evaluated by doctors Sunday in New York.

The trade was made one day after the Mets bullpen nearly wasted Pedro Martinez's longest outing of the season in a 7-4 victory over Pittsburgh.

New York took a 7-1 lead into the ninth inning, but the Pirates scored three times against rookie Eddie Kunz. Pittsburgh brought the tying run to the plate against Pedro Feliciano, who retired the final two hitters to earn the save.

The 25-year-old Hernandez hit .138 in 35 games with the Mets from 2005-07, and was batting .203 with five homers and 36 RBIs in 125 games this year at Triple-A New Orleans.

Hernandez hit .301 in 128 games at New Orleans last year and would provide depth at shortstop for Washington.

The Nationals' starting shortstop, All-Star Cristian Guzman, missed his third straight game with a sore left thumb Sunday. Backup infielder Alberto Gonzalez went on the DL Aug. 14, retroactive to Aug. 5, due to a left hamstring strain.