NEW YORK -- Andy Pettitte's sleep is sure to be elusive on Friday, the left-hander said, as he'd lie awake and rue a lapse in judgment to the frailest of Mets batters.

A home run by 165-pound reserve outfielder Endy Chavez was the difference as the Mets downed the struggling Yankees, 3-2, sending the Bombers reeling to their sixth loss in eight games.

"It's going to be a rough night," Pettitte said.

The loss, in the Yankees' shortest game of the year at two hours, 18 minutes, dropped the team to 10 games behind the rained-out Red Sox in the American League East, four games under .500 at 18-22.

The 10-game deficit is a new low for the Joe Torre era, surpassing a previous 9 1/2 game pursuit of the Orioles back in Sept. 1997.

The game's decisive blow came in the fifth inning at Shea Stadium, with Pettitte grappling to hold a one-run lead and deliver the Yankees the type of lengthy pitching performance that has been fairly common of late, if not always victorious.

Mets catcher Paul Lo Duca opened the inning with a double to left, one of a pair of two-base hits on the evening, bringing up Chavez -- a speedster with sparing pop, best known for a stunning defensive play that stole a home run in last year's National League Championship Series.

Deception, it turns out, is also part of Chavez's repertoire. With the left-handed Chavez waiting on a 1-0 offering, Pettitte considered the situation and anticipated that Mets manager Willie Randolph might order a sacrifice to move Lo Duca along to third base.

As it later turned out, Pettitte was half correct -- the sign had been on, but only for the first pitch of the at-bat. When Pettitte reared back and threw a high and inside fastball, hoping to induce Chavez into an infield pop, he fired right into Chavez's green light.

The two-run homer would eventually send Pettitte down the clubhouse runway in a fit of rage, and later, Pettitte promised a red-eyed night in a bedroom somewhere north.

"It's about as frustrating as you can get," Pettitte said.

Factoring in a first-inning sacrifice fly to Carlos Delgado, Pettitte's evening would be recorded as a quality start.

The 34-year-old southpaw, who came into the game with the fourth-highest winning percentage among active pitchers against the Mets, allowed just five hits over seven innings, walking one and striking out four.

"He made one mistake," catcher Jorge Posada said. "That's it. That's the difference in the ballgame. You've got to live with that."

Not that it would be easy. The home run by Chavez was striking because it had been the first Pettitte had allowed to a left-handed hitter in a span of 23 starts, dating back to last year with Houston, when he surrendered a blast to Chicago's Scott Podsednik.

But it may not have been all that shocking to the snake-bitten Yankees, who had spoken optimistically that the frenzied atmosphere of the Subway Series might shake up their offensive doldrums.

Instead, the Yankees managed just two runs -- both coming on a fourth-inning home run by outfielder Hideki Matsui -- as their slumbering offense waits for the day when everything begins to click again.

The Yankees have longed often for a big inning that breaks them free from their offense purgatory, and though they've had a few flashes of late -- the last coming as they batted around in a four-run ninth inning Wednesday at Chicago, pummeling youngster Andy Sisco -- nothing has seemed to have the staying power the Yankees desire.

"The spark is there," Torre said. "We just have to make it show up on the scoreboard."

So it was as the Yankees quietly settled back to the usual score against Oliver Perez, a 25-year-old left-hander with outstanding stuff and unreliable consistency that prompted the Pittsburgh Pirates to abandon him as their one-time staff ace.

But Perez had enough to stifle the Yankees and earn a standing ovation from the home crowd, holding the Yankees to five hits and two runs, walking two and striking out five. Joe Smith recorded the final out of the eighth and Billy Wagner finished off the Yankees in the ninth inning for his 10th save, striking out pinch-hitter Jason Giambi in a hard-fought nine-pitch at-bat.

"We just can't seem to get over the hump, as far as getting that big run to break us through," Giambi said.

Earlier this season, when the offense seemed to be blasting away in support of inconsistent starters, it seemed to be an equation rooted in agony.

But as Torre's Yankees have found the last week or so -- New York has been held to two runs or less in five of the last eight games -- the mirror image is much more unpleasant to deal with.

"This is probably more frustrating," Torre said. "It was a given for us that we were going to score runs."

The only measures of consistency, it seems, have come from Derek Jeter and Posada, who continue to rattle off hit streaks -- both at 13 after Friday -- in the hopes that some of their teammates will find the way to join them.

Jeter said he had no doubts the Yankees could -- and would -- play better. He scoffed at the notion that this might be as good as the Yankees could do.

"If that's the case, you should go home," Jeter said. "You don't ever say that this is as good as it gets. Around here, people have a lot of confidence. We can play."

As Torre exited the clubhouse in his street clothes late Friday, he made a point of stopping at Matsui's locker. Matsui's English has improved markedly since he arrived in the United States in 2003, to the point where he often no longer requires the services of his translator, Roger Kahlon.

But Torre's message needed no interpretation, though it offered one. Tapping Matsui on the right shoulder, Torre glumly offered a thumbs-up before departing Shea Stadium for the evening.

With a 2-for-4 performance, maybe Matsui's effort was reason enough for Torre to hope there was a corner approaching, about to be turned.

At this point, it seemed to be worth a shot.