SAN FRANCISCO - As the Mets constructed their team during the offseason, they envisioned a lineup based on length from top to bottom, with enough firepower to thrive.

Instead, injuries have left gaping holes in the lineup, which has been made even worse by the lack of production from the players who have managed to stay healthy.

In particular, the Mets' offensive woes can be traced to Michael Cuddyer and Lucas Duda, who had been expected to anchor the middle of the order.

Cuddyer, 36, was hitting .236 with six homers and 28 RBIs before going 2-for-4 last night, including a single that triggered a three-run ninth inning in the Mets' 3-0 victory over the Giants. Duda struck out as a pinch hitter in the ninth. His slide has dragged his average down to .248 with 10 homers and 34 RBIs.

"It's been a grind, there's no secret to that," said one-time batting champ Cuddyer, who has faltered after signing a two-year, $21-million deal. "The results aren't what I expect, what the team expects or what everybody else expects, either. The only thing I can keep doing is working and going out and playing."

Duda's recent struggles prompted Terry Collins to bench him for Monday night's series opener against the Giants.

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"He's swinging at balls out of the zone," Collins said. "He wants to hit the ball out of the ballpark. You look at the games in Los Angeles, the pitches he got he could drive, he fouled them off. As we all know, those are the pitches, we can't miss those. That's where you've got to do your damage."

Duda enjoyed a breakout season last year, hitting .253 with 30 homers and 92 RBIs. But since June 17, he's hitting .136 (9-for-66) with 26 strikeouts in 19 games. He hasn't homered since June 18.

"It's a little different situation these days with Lucas because he is a huge part of our lineup," Collins said. "He's had to work his way into that role and now he is a big, big part of our lineup. We've got to have his offense, we've got to have his power. But nobody works harder."

Cuddyer's tailspin has been equally costly for the Mets, whose 3.49 runs per game ranks second to last in the National League. That offensive failure has been amplified because it has wasted an outstanding season by the pitching staff. Mets pitchers have limited opponents to 16 earned runs in the last 107 innings, a 1.35 ERA.

Cuddyer was hitting .273 after going 2-for-4 on June 6. Since then, he is hitting .160 with four doubles, no homers and four RBIs in 24 games.

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"My swing feels good, my swing feels the same," he said. "But whether it's I'm expanding the zone or whether I'm pressing, whatever the case may be, the production's not there. It's not where I expect it to be."

The Mets signed Cuddyer despite concerns about his health. Though he missed four starts with a knee injury, he has stayed in the lineup.

That durability stands out, especially given that the Mets have gone a large chunk of the season without David Wright, Travis d'Arnaud and, until recently, Daniel Murphy.

But Cuddyer has yet to parlay his health into production.

"Just play, there's no secret formula," he said. "Just keep going out there and play the game. That's it."