MILWAUKEE -- It could not be a worse time for the Milwaukee Brewers to experience this particular variety of déjà vu. After the most recent tweak in a career marred by unusual injuries, right-hander Ben Sheets insisted there was no need for such sentiment.

Making their strongest push for the franchise's first playoff berth since 1982, the Brewers held their breath as Sheets left his start early with left groin tightness, and the Mets pounced late on the Brewers bullpen to churn out a 4-2 win on Labor Day. Sheets did not seem worried about the ailment after the game, which took precedence over the outcome.

"I think it's going to be fine," Sheets said. "I don't think it's as bad as last year, and I thought I could make my next start last year. I really think I'm going to be alright. I'm just going to pay a little more attention to it and hopefully move forward."

Sheets left after throwing only 54 pitches through five innings, allowing no runs on two hits. But the four-time All-Star said his stuff was subpar and his velocity was down ("Those were heaters," Sheets said, when asked if he used more changeups than typical).

Sheets is enjoying his healthiest season since 2004, with injuries to his inner ear, back, finger, hamstring and groin littered in between. He left a start in early 2007 with a pulled groin, as well.

"It's the total opposite leg, for one," Sheets said. "I felt it actually pull last year. This time, it really just kind of cramped up on me. There's greater prizes down the road we hope we can get to [instead of taking a risk], and we feel we have a good enough bullpen to hold most of those games."

Not on Monday. Carlos Delgado lifted a two-run homer in the eighth against Eric Gagne (4-3), and Ryan Church later added an RBI double to turn a 2-1 Milwaukee lead around. The rally knocked Sheets out of a chance to accumulate his career-best 13th victory.

"We had the right guy in the right situations in the end," said right-hander Carlos Villanueva, who had to work out of his own jam after entering the game in the sixth. "We'd been solid. It's the first game of the series, and we can still win this series."

Milwaukee had done just enough against former Cy Young winner Johan Santana to deny him his own 13th victory while the Mets offense labored against Sheets. Santana's changeup proved effective as he struck out 10 batters during his stint, part of the Brewers' 15-strikeout day.

"They're an aggressive team," Santana said of his change. "You have to show them you can throw the pitch and keep them off balance. "

Said Brewers manager Ned Yost, "Every once in a while, you've got to have the pitching to win a 2-1 ballgame, and we didn't do that today. We matched up against one of the premier pitchers in the National League, and you know there's not going to be a lot of runs. We were doing everything we could to keep that game at one or two runs and were just unsuccessful."

Villanueva put runners at the corners with one out before escaping the sixth, and two David Riske walks set up a bases-loaded situation in the seventh. Mitch Stetter's wild pitch brought home a run that cut Milwaukee's lead to 2-1, but Stetter retired Jose Reyes to preserve the temporary lead.

Gagne allowed a leadoff double to Daniel Murphy and struck out David Wright before missing his spot badly on an 0-2 pitch, and Delgado parked it for his 31st home run of the year.

"He was trying to make an 0-2 pitch and he just didn't make it; he got too much of the plate," Yost said. "It wasn't a pitch he was trying to throw a strike on. He just didn't hit his spot."

The much-maligned Mets bullpen did its job, retiring nine of 10 batters after Santana allowed two runs on seven hits in six innings. The Brewers were fortunate to get a second tally across against the left-hander, when a balk drove home a critical tally.

Prince Fielder and Corey Hart led off the sixth with back-to-back singles, and runners were at second and third with Santana ahead of Bill Hall, 0-2. Santana stepped off the mound with the wrong foot to bring Fielder home via a balk, though Hall later struck out to prevent further damage.

Sheets was gone by then, after feeling the tightness materialize warming up for the third inning. He said smart pitch selections by catcher Jason Kendall and good location allowed his day to last as long as it did.

"That's what good location will do for you," Sheets said. "I think that might be the first time I didn't have a strikeout through five, but that's the way it goes. I got outs, I just didn't get enough outs."

Ryan Braun finished the day with three hits, including an RBI double in the first. Nelson Figueroa (3-3), a former Brewers pitcher, worked a clean seventh to earn the victory, and Luis Ayala earned save No. 4.