"We're all behind Billy," Delgado said. "He's going to save a lot more games than he's going to blow. We want him on the mound every night in the ninth inning when we've got a lead. It's as simple as that."
Substitute outfielder Endy Chavez sparked New York's offense from the No. 8 spot on a rainy night at Shea Stadium, and Delgado drove in two runs.
Handed a 3-1 lead in the ninth, Wagner walked two and then gave up consecutive RBI singles to Jose Hernandez and Ronny Paulino with two outs. Wagner, who signed a $43 million, four-year contract in the offseason, has three blown saves in 10 chances.
"Pedro pitched a great game, the team played well and I didn't do my job," he said. "Tonight I beat myself, and that's what's frustrating."
His latest failure prevented Martinez from becoming the first six-game winner in the major leagues. Martinez fanned nine in six sharp innings and was one out from winning his first six starts for the second time in his career.
"Billy is the same regardless of what happened. I know he probably doesn't feel as good as he would like to, but he battled," Martinez said. "He's going to be right out there tomorrow and ready to go."
Jose Reyes hit an RBI triple and Delgado had a run-scoring double for the Mets, who sent Pittsburgh to its 14th loss in 16 road games this season. The punchless Pirates (8-21) have scored three runs or fewer in 15 of their past 17 games.
"We are giving ourselves opportunities to win," manager Jim Tracy said. "They got a big hit we were not able to get, but we want to be in positions like we were in tonight."
Delgado drove a 1-1 pitch from Mike Gonzalez (0-2) over the left-center fence for his 11th homer.
"I threw him a fastball. It was down and away. He just went down and got it," Gonzalez said.
With his 380th career homer, Delgado passed Hall of Famers Tony Perez and Orlando Cepeda.
"I'm flattered," Delgado said. "But the way I look at it, I've got a few years left."
It was his fourth game-ending shot and first since July 8, 2004, with Toronto against Seattle.
"Best feeling in the world. You can jog around the bases and nobody can get you out," he said.
Chad Bradford (1-1) pitched two scoreless innings for the win.
With a steady rain falling from the third through the seventh, Martinez held Pittsburgh in check on only three hits.
Chavez started in right field as Xavier Nady was rested. Chavez went 4-for-5 with two doubles and a spectacular, diving catch in the 11th. By the late innings, a sparse crowd thinned by the rain was chanting "Endy! Endy!"
Mets manager Willie Randolph explained before the game that he likes the way Chavez is swinging the bat and he liked the matchup against starter Ian Snell.
Chavez has 10 hits in his last 16 at-bats (.625). NL East-leading New York has won six of eight.
"The best part of the night is that we got the job done," Chavez said.
Martinez allowed only a solo homer to Freddy Sanchez in the first. The right-hander walked one and left for a pinch-hitter after 77 pitches.
With the score tied at 1, slumping slugger Cliff Floyd singled through the soggy infield to start the sixth and moved up on Ramon Castro's sacrifice. Chavez hit a sinking drive to left-center that glanced off the glove of diving left fielder Jason Bay for an RBI double.
Floyd scored with a slide and then stood up, covered in mud.
One out later, the speedy Reyes hit a liner down the right-field line and practically splashed his way around the bases for a run-scoring triple that made it 3-1.
Sanchez connected with two outs in the first. Kaz Matsui doubled in the bottom half and scored on Delgado's two-out double to left.
Snell fanned a career-best nine in 5 2/3 innings. He allowed three runs and seven hits.
"Pedro Martinez had a terrific changeup and curveball. There was really very little opportunity to do anything offensively," Tracy said. "We did some terrific things in the ninth inning when we got the two big hits to tie the game."
- Martinez won his first eight starts with Montreal in 1997 en route to the first of his three Cy Young Awards, according to the Elias Sports Bureau.
- Mets reliever Duaner Sanchez threw a hitless 10th, extending his scoreless streak to 21 innings dating to last year with the Dodgers -- including 18 this year.
- Pittsburgh RHP Roberto Hernandez, who had a strong season as a setup man with the Mets last year, worked a hitless 10th.
- The four hits matched a career high for Chavez, done four times previously. The last was in September 2004 with Montreal.
- The Mets announced that fans can exchange their stubs for free tickets to a June game against Cincinnati.