Jose Reyes added a two-run triple and Endy Chavez had four hits for the surging Mets, who have won 14 of 17. One day after gaining sole possession of first place for the first time since April 19, New York played as though it plans to stay on top the rest of the way.
"Now, we're starting to play consistent baseball," Reyes said. "That's what we didn't do in the first half."
Coupled with Philadelphia's loss at home to Atlanta, the Mets' victory gave them a two-game cushion in the division -- their largest since an embarrassing collapse last September.
The Mets roughed up rookie Mitchell Boggs (3-2) for the second time in 22 days, handing the Cardinals their fifth straight defeat. Milwaukee finished a four-game sweep in St. Louis on Thursday night, the Cardinals' first four-game skid of the season.
"There's nothing wrong with the way we competed," manager Tony La Russa said. "I give Pelfrey credit. He's in a good run and he made some good pitches."
Argenis Reyes hit his first major league homer and drove in two runs as the Mets won for the 10th time in 11 home games. David Wright got New York started with an RBI double in the third off Boggs, who gave up 10 earned runs over six innings in his previous major league start, an 11-1 loss to Pelfrey on July 3.
Boggs was optioned to the minors three days later, then recalled on Monday to fill a hole in St. Louis' injury-depleted rotation.
"They saw me throw a lot of pitches early in the game, so it was easy the third time around," Boggs said. "I was familiar with them and they were with me."
Pelfrey (9-6) pitched seven strong innings, allowing one run and seven hits. He struck out five and walked none.
The 6-foot-7 right-hander has quickly become a force, going 7-0 in his past eight starts. He hasn't lost in 11 outings since May 26 against Florida.
"The biggest thing is confidence. I'm out on the mound and I don't feel like I have to be perfect," Pelfrey said. "I believe in myself that I'm going to win."
Pitching more aggressively, Pelfrey has lasted at least seven innings in his last five starts. He's walked only one batter over the past four.
"He's fun to catch right now," New York's Brian Schneider said. "Everybody knew he was going to make adjustments and make the transition, but I don't think anyone thought it was going to be this quick. He's a completely different pitcher than he was on opening day. ... Lights on, lights off."
New York needed four relievers to close it out. Duaner Sanchez let all three batters he faced in the ninth reach safely -- just as he did when the Mets blew a three-run lead Tuesday night against Philadelphia.
St. Louis slugger Albert Pujols went 0-for-5 with three strikeouts and grounded out with two on to end it.
"He had a tough day," La Russa said. "It happens to all of them."
Reyes' two-run triple to right-center with two outs in the fourth made it 3-0. Delgado added a two-run shot off Boggs in the fifth, his 20th homer this season and ninth in 25 games.
After slumping for much of the year, Delgado is batting .390 with six home runs and 18 RBIs in July.
"I never really doubted myself, that I couldn't hit anymore," Delgado said. "We did a lot of good things. It started with Pelfrey. He set the tone."
Cardinals RHP Chris Carpenter, the 2005 NL Cy Young Award winner, was scheduled to make a rehab start for Triple-A Memphis on Friday night and could return to the rotation soon. ... Mets RF Ryan Church (post-concussion syndrome) was cleared to begin light conditioning work but is not expected back before Thursday's trade deadline. "This time around, I didn't have any problems," Church said. "There's no limitations."