New York ? Mike Piazza will be back in the Mets lineup Tuesday night and the infusion of his monster bat couldn’t come at a better time. The Mets are going from playing baseball’s worst team, the Brewers, to the defending champion Diamondbacks, who are tied for first with the Dodgers in the NL West.

The three-game series kicks off Tuesday night in Phoenix with Al Leiter opposing Rick Helling at BankOne Ballpark.

Piazza has been on the shelf since grabbing his left hamstring legging out a single in the first inning against the Cardinals on Tuesday. Though Piazza said he was available to pinch-hit over the weekend, Bobby Valentine gave him more time to recuperate.

Over the weekend, Piazza tested the injury by catching Leiter’s bullpen session and taking batting practice. The real question is how the hamstring will stand up to running.

“It’s getting to the point where you test it,” Piazza said.

Centerfielder Timo Perez, who also hurt his left hamstring Tuesday, might also play. His only action since the injury was a pinch-hitting appearance Sunday. He could be back in center, or Valentine may opt to stick with Jay Payton, whose bat began to come around with Perez out.

The Mets are in a better situation than when Piazza grabbed for that hamstring, winning five of their last six to share first place with the Expos in the NL East.

They’ve found some good chemistry with Roberto Alomar batting leadoff the past four games, all wins. And they’ve shown they can win in a variety of ways, at times with great starting pitching, at others with awakening bats.

“They guys who are struggling are starting to swing the bats real well,” Alomar said. “It’s a good sign. You get one hit, but maybe it’s a big hit. The offense could start coming alive (with Piazza back).”

Said Valentine: “I like where they are right now. They’re playing a hard brand of baseball and playing it for all nine innings.

“I think we’re building well.”