ON JULY 8, in the second game of a two-ballpark double-header between the Mets and the hated Yankees, Roger Clemens sent a fastball in the direction of Mike Piazza’s head.

The next thing you know, Steve Phillips was kicking anyone in pinstripes out of the Shea Stadium weight room and changing travel arrangements for the All-Star Game.

Last night, Jay Bell, in the fourth inning of a game against the laid-back Diamondbacks, sent his forearms in the direction of Mike Piazza’s face.

He knocked Piazza’s mask in one direction, his Adam’s Apple in another, and his back straight down to the hard ground behind home plate.

Do you think Phillips will be barring Curt Schilling from the Mets’ weight room today?

For a team that practically put a bounty out on Clemens, the Mets were surprisingly placid toward Jay Bell.

What makes him so special?

The fact that he wears wire-rimmed glasses, giving him the appearance of a CPA in double-knits? Or that he is only 6-foot-0, 184 pounds? Or that he plays for a team that, with the exception of last night’s 5-1, 10-inning loss, the Mets can’t seem to lose to?

Is it simply that Bell is not a Yankee?

Face it, what Jay Bell did to Mike Piazza last night was every bit as blatant as what Clemens did back in July.

In fact, it was probably more so, since no one can say with any certainty that even a future Hall of Famer like Clemens can be absolutely sure where the baseball is going on any given pitch.

But you’re darn tootin’ that Jay Bell can pretty much pinpoint where he would like to place his forearms at any given moment on any given day.

There was no doubt about what Jay Bell did last night, or what he was trying to do.

He was going for Mike Piazza’s head, which was up there like the Statue of Liberty after Jay Payton threw him a hospital pass from center field.

Piazza, his concentration on the approaching baseball, made the grab and the pivot. There was Bell, in full charge, his arms not only upraised but extended in the maneuver football coaches like to call the forearm shiver.

And everybody in Shea shivered when Piazza toppled over, clutching at his throat.

Losing the game is one thing. The Mets came in with a 51/2-game lead over the Diamondbacks for the NL wild-card spot and were still very much in the race for the NL East, a mere two games behind the Braves.

Losing Piazza, however, is something else. Lose him and you lose October.

And yet, not a single Met climbed to the top step of the dugout when Piazza went down, with the exception of Bobby Valentine, who is always there anyway.

Not one of the four Mets pitchers threw a pitch anywhere near Bell’s anatomy. In fact, they allowed him to get so comfortable I think he planted a flag in the batter’s box. Today, he may start installing a swimming pool.

And in the clubhouse, no one had much to say about a play that very well could have robbed them of the only player capable of carrying them to the World Series.

“Clean play,” said Bobby Valentine. “I think it’s an automatic reaction to throw your arms up like that.”

“It was clean,” said Payton. “You have the option to slide or to try to take out the catcher. He chose to try to take him out.”

“I was sitting next to [Todd] Pratt and he said it was a clean play,” starter Bobby Jones said.

Piazza, a millionaire’s kid from a Philadelphia suburb who internalized more than a little SoCal Cool from his days as a Dodger, did his best to play off Bell’s play, too.

“I thought the forearms were a little high,” Piazza said. “I don’t like it, I’m not happy about it, but what am I gonna do? I’m not gonna cry about it.”

Truth is, without Piazza the Mets don’t move very far.

That’s why when you have a weapon like him, you protect him the way a hunter protects his favorite rifle in a velvet-lined case.

Already, the Mets are aware that the demands of catching 140-plus games a season is a major drain on Piazza, who by playoff time last season was pretty much a spent bullet.

And the very best way for the Mets to have helped Piazza last night would have been to win the game.

But they could only manage five hits, and Piazza had three of them. One of them, his 33rd home run of the year, came in the sixth inning, two innings after he was laid flat by Bell.

That was the same way Piazza reacted to the Clemens beaning, and it is pretty much the same way he reacts to everything.

Piazza’s homer gave the Mets a temporary 1-0 lead, a lead Jones promptly gave back.

Then, Rick White gave the game away in the 10th, allowing a one-out double to – who else? – Jay Bell that sparked a four-run inning.

What could have been a significant night for the Mets instead became a needless, and nearly disastrous – defeat.

A win would have opened a 61/2-game lead over Arizona for the wild card and cut the Braves lead to a single game. That would have pretty much assured the Mets of October baseball with five weeks left in the regular season.

That, in turn, would have meant more days off for Piazza.

Instead, he will take today off and go back to work.

“That’s what makes Mike so great,” Payton said. “A lot of guys might catch that ball and back up, or choose not to take the hit. Mike stepped up.”

In this case, that’s more than can be said for any of his teammates.