After forcing out the Braves' Jason Heyward at second base,...

After forcing out the Braves' Jason Heyward at second base, Luis Castillo fumbles an exchange on a double play, which opened the door for two key runs by Atlanta in the first inning. (Aug. 2, 2010) Credit: AP

ATLANTA - The easy scapegoat for the Mets' 4-1 loss to the Braves last night at Turner Field was Luis Castillo. It was his fumbled relay on a key double play in the first inning that opened the door for two huge runs in an anticipated pitchers' duel between Johan Santana and Tim Hudson.

But the Mets' issues extend beyond Castillo's suspect hands, and manager Jerry Manuel suggested as much after criticizing the former Gold Glove second baseman for his costly gaffe.

The return of Castillo, along with Carlos Beltran's comeback after the All-Star break, has messed with this club's winning formula, which once had the Mets at a season-best 11 games over .500 (43-32) on June 27.

Since then, they are 10-21, and last night's loss dropped them back to .500 (53-53) for the first time since June 2. The Mets also are in fourth place for the first time since May 29 and trail the division-leading Braves by 71/2 games. The question on everyone's mind at this moment is why.

"I think the pieces are a little different," Manuel said. "I'd have to say that. Maybe they're not quite as right as they should be at this point. Obviously, they're very, very good players. But right now, it's just not working."

With exactly two months left in the season, the negative effects do not appear reversible. Beltran drove in the Mets' only run with his fifth-inning double off Hudson (12-5), but the team was 1-for-9 with runners in scoring position.

With two on in the fourth, Castillo struck out looking after trying to draw a walk in front of Santana, who also whiffed to end the threat.

Maybe that spot would have enabled Castillo to atone for his earlier mistake, but his defensive problems are not limited to one isolated incident. Castillo has botched a handful of double-play exchanges since returning from a six-week stay on the disabled list, and his confidence appears to be wavering.

Immediately after the game, bench coach Dave Jauss counseled Castillo at his locker, but that didn't do much to improve his mood before he glumly spoke to reporters.

"I feel bad because I know I can do a better job than what I'm doing," Castillo said. "I'm trying so hard and nothing good is happening. I have to try to change it and see what happens."

The same thing can be said for the sinking Mets as they begin a crucial road trip through Atlanta and Philadelphia. Manuel again shuffled the lineup for last night's game, moving Beltran into the No. 3 spot ahead of David Wright, but it did little to revive the offense.

After the game, Manuel huddled in the manager's office with general manager Omar Minaya and assistant GM John Ricco, but it seems as though answers are in short supply.

The Mets passed on making a trade last weekend to improve the club, then watched as Rick Ankiel - acquired by the Braves before Saturday's deadline - drove in two runs with a first-inning single.

For Santana (8-6), it was a little too similar to his previous outing, when he allowed six first-inning runs in an eventual 8-7 loss to the Cardinals. This time he put the Mets in a 3-0 hole in the first inning, then allowed only Chipper Jones' solo homer in the next six. Pitching just well enough to lose is a familiar storyline this season for Santana, who suggested that the Mets still have the ability to rebound.

"I'm confident," said Santana, who had a season-high 11 strikeouts. "That's the kind of mentality we've got to have around here."

And do the Mets have it? "I don't know," Santana replied. "I don't tell them what to do. I don't judge my teammates. We're all here together and all on the same page. We have to keep playing and hope this will turn around."