MLB

CHEMISTRY IS KEY FOR AMAZIN’ RUN

THE Mets have emerged from both last September’s greatest late-season collapse in baseball history and the swill surrounding the first three months of this season to establish themselves as sports’ true Redeem Team.

They have emerged from the darkness, winners of 10 of their last 11 and 30 of their last 43, with Johan Santana spinning seven shutout innings in last night’s 3-0 triumph over the Astros. They lead the division by 2 1/2 games over the Phillies.

“I hope we all have last year in the back of minds to serve as a motivating force down the stretch,” David Wright said. “But I think this stretch of baseball has officially ended any negative impact that might have carried over into the season.”

In other words, there is a bright light at the end of the tunnel. Now the Mets have to hope against hope that the light isn’t from an onrushing train disguised as Luis Castillo.

Chemistry is a fragile thing in sports, an intangible that’s often more easily identified in its absence than in its presence. Jerry Manuel tried to explain how he sees it.

“You would hope that chemistry would not be determined by winning, but that it is defined by having enough faith in the person next to you to embrace him when he is struggling,” the manager said. “I believe our team has that chemistry.”

Now, though, the bonding that’s taken place in the post-Willie Randolph era – let’s face it, deserved or not, Randolph had become the face of Mets failure the way Gene Mauch was always the personification of the Phillies’ 1964 debacle – will be tested.

It won’t necessarily be tested by external forces, but rather from within when Castillo returns from the disabled list today to immediately reclaim the job at second base, which has been handled so well in his absence by Damion Easley and Argenis Reyes.

Manuel understands that he won’t only be shaking up the lineup that has gone 47-28 with Easley or Reyes starting, but he – or his organization superiors – will be shaking up the roster that been cooking just fine as it is. Someone will have to go to the minors, even if only until the roster expands on Sept. 1.

Someone who doesn’t deserve to sit will sit – Easley, primarily – and someone will doesn’t deserve to go down will be demoted – Reyes, probably – in order to accommodate Castillo. Castillo was a significant disappointment and more than a bit of a whiner before going on the DL with a hip flexor on July 3, and is also only five months into the four-year, $25M contract he received from GM Omar Minaya this offseason.

“These are very, very, very tough decisions,” Manuel said. “This is a difficult situation even for [Castillo]. We’ve played extremely well without him, we’ve put ourselves in the pennant race. He wouldn’t want to mess that up for the team. It’s kind of touchy.

“But Luis is a [one-time] world champion who is accustomed to winning, so you can’t dismiss that, as well.”

Castillo does have a championship pedigree he earned with the Marlins in 2003. Still, that didn’t help the Mets at all last year when he came to New York from Minnesota. The Mets not only had that September anyway, but were 23-25 when he started last year and are 30-34 when he’s started this season.

And they are 31-14 since Castillo went on the DL.

No, he’s not an NFL quarterback or an NHL goaltender with more than his share of the burden on his shoulders. The starting rotation has remade itself into a dominating force in his absence. Carlos Delgado has turned back the clock.

Still, if you are what your record says you are, the Mets clearly are a better team without Castillo than with him. So why tempt fate?

larry.brooks@nypost.com