MLB

Manuel’s juggling act a matter of survival

Jerry Manuel now faces the easiest tough decision of his career.

Carlos Beltran will return to the Mets’ roster to open the second half and Manuel already has installed him in the cleanup. Beltran’s return gives the Mets four outfielders for three spots, a bit of math that might only work if there were a designated hitter in the NL or the metric system had ever caught on in America.

This is supposed to be a conundrum for Manuel, a puzzle that threatens the harmony of his clubhouse and the fluidity of his lineup. Except it is none of that. Especially not for Manuel.

BOX SCORE

The Mets manager was still joking yesterday that, not long ago, he imagined packing all of his stuff for the series that opens Thursday in San Francisco, making it an easy transition to his Sacramento, Calif., home when the inevitable firing arrived.

Manuel understands the rules of engagement. He is 56 and without the kind of distinction to think another organization would ever hire him to manage. He has just an option with the Mets for next year, nothing guaranteed. So there is this season for him and nothing else. That is why he pitched the heck out of Fernando Nieve early and Bobby Parnell recently. It is why he used Jose Reyes as strictly a righty hitter, to heck with the oblique injury and Prevention and Recovery.

And it is why when the second half opens, Beltran will be hitting cleanup, Jeff Francoeur will be on the bench and Jason Bay should be watching his back. The only season that matters to Manuel is this one. If he retains his job, he will take any offended souls out to the finest restaurant in Port St. Lucie — I believe that is Chili’s — and do a mending job in February 2011.

“Whoever is playing well will play the most,” Francoeur said. “And that is the way it should be.”

Manuel might do some feeling out early before introducing a full meritocracy. He has to let Beltran, who has not played a major league game since Oct. 4, work through some rust. He promised Francoeur starts against San Francisco’s two lefties, Jonathan Sanchez and Barry Zito.

But as Manuel said after the Mets’ 3-0 win over Atlanta yesterday: “I’m going to try to give them all as much time as possible. Then I’m going to do what’s best for the team — who is playing the best. We’re in a pennant race and whatever pieces fit, we have to put them out there.”

In fact, Manuel revealed just how much current events will influence this decision just yesterday. Before the game, he indicated Angel Pagan would play against righties, Francoeur against lefties and Bay would be his everyday left fielder. But then Pagan produced three more hits, and excellent catches to end the first inning and the game. Alex Cora called Pagan “our first-half MVP” and after the game, Manuel was promising to play him pretty much every day.

He did not offer the same sentiments for Bay, saying: “I don’t know right now. I want to take these three days before I come up with that.”

Bay did not start yesterday on his bobblehead doll day as Manuel decided to give the slumping left fielder “time to exhale” and time away from the Citi Field booing. The $66 million man is currently parked on six homers — as many as he hit against just Toronto last year for the Red Sox. Maybe he has a 15-homer second half approaching. Maybe Beltran will quickly revert to star level. Maybe Francoeur will stay as magnanimous as he was yesterday about probably being the odd-man-out.

“I’m a big boy,” he said. “It is not like I didn’t see this coming.”

But if Bay doesn’t hit or Beltran needs a caddy to protect his knee or Francoeur whines, Manuel is simply going to stress self-preservation and play the lineup he feels will help the Mets win. That ideally fits the desires of Mets ownership anyway because the franchise so badly needs a pennant race for ticket sales and the playoffs for credibility.

So Beltran rejoins the lineup Thursday, complicating the math. Except Manuel is not going to overthink it when he has just one thought on his mind: Survival.

joel.sherman@nypost.com