THAT KID named Nestor is proving to be quite the vital cog for Monsignor Bonner High's baseball team.

It's rather surprising, too, considering he stands about 3 feet tall.

Say what? Joe Nestor, who yesterday pitched the Friars past Central, 11-4, in steamy weather at La Salle High for the District 12 Class AAAA City Title, appeared to be a lot taller than munchkin material. 'Cause he is, at 6-3 and 205 pounds.

Right about now, though, Joe is sharing the Nestor spotlight with his 6-year-old brother, George, the team's batboy.

"When we asked for permission for him to be the batboy," Joe said, "it was going to be for only one game. But we won, so . . . "

Come back any time, Georgie buddy!

"He has been to almost every game since," Joe said. "Out of the four we've lost, he didn't go to three of them. He goes to all of them now. Even gets out of school early sometimes.

"Bonner baseball is all he talks about. All day. Every day. He knows every player. They all come over to him on the bench, to mess around with him. They even have special handshakes. He loves this."

On Tuesday, after Bonner bested Archbishop Ryan, 13-3, in five innings, to capture the Catholic League championship, as part of their celebration, the Friars handed George the plaque, hoisted him high and belted out the Happy Birthday song.

"He's still talking about that," Joe said, laughing.

Hmm. Maybe George wants to be quoted in a major metropolitan newspaper. Let's corner him.

Hey, George, your brother did pretty well today, right?

All he did was hold out his hands in palms-up fashion, as if to say, "How I am supposed to know? I'm only a 6-year-old batboy. Go bug somebody else."

Actually, Joe Nestor's performance was something of a mixed bag. The lefty pitched one-run ball over his final four innings of work, through the fifth, and those results were quite different from the first inning, when he was touched for three runs on four hits, two of the ringing variety (RBI doubles deep into outfield gaps).

Suddenly, Nestor looked a lot like Bill Murray. And the game was resembling a diamond version of Groundhog Day.

The Friars had also tumbled into a 3-0 hole in the first half-inning of the CL final.

"I didn't think about that too much while the inning was going on," Nestor said. "But I did as soon as I got to the dugout. Some of the guys were even joking about it. Coach D [Joe DeBarberie] said to me pretty much the same stuff he said the other day to Anthony DiGalbo - 'Don't let them get anything else.'

"That was all my fault. They were hitting fastballs down the middle. Real meatballs. I just had to do a better job."

He was OK, he insisted, in terms of mind-set, despite the early rock-around.

"Last year, I pitched for Upper Darby High," he offered. "A first inning like that would have turned into a loss. Now, I'm a lot more comfortable when we're down. I trust in our bats. I just had to make better pitches and depend on my fielders."

Bonner committed just one error, and it didn't figure into the scoring. The defensive highlight came in the second inning, when Rick Reigner made an impressive, coming-forward, diving catch in center.

With help from a crafty changeup, Nestor struck out seven in his stint. Matt Dolan and Jim Bonner followed with one hitless inning apiece.

The Friars tallied five apiece in the third and fifth and one in the sixth. Overall, Reigner (triple), Alex Liberatore, Paul Shepherd and Mike Haley posted two hits apiece and the first three added one RBI each. The most damaging hit was Matt Ruggieri's two-run double to left-center in the fifth.

Pete Rowe (3-for-3, RBI double) and losing pitcher Kevin Pfeifer (2-for-3, double, two RBI) were Central's big guns. Adam Hoskins, normally the cleanup hitter, was held out for the first two innings by coach Rich Weiss upon arriving after the scheduled reporting time.

Central's senior prom was last night. Hoskins had been running late errands, in preparation, Weiss said.

Nestor said he transferred to Bonner mostly because he was good friends with so many of the players from outside ball. Also, he figured the Friars' coaches would be able to help him find a suitable college. He's headed for La Salle and hopes to make the team as a walk-on.

If you're a veteran follower of Bonner sports, the Nestor surname should be familiar. His cousin, Mike, was a basketball star (Class of '95, third team Daily News All-City) and then enjoyed an excellent career at Shippensburg, where he's now an assistant coach.

Joe ignored those bloodlines. Never opted for football, either, despite the sizelines.

"Baseball's really the only sport I ever cared about," he said.

George is showing similar traits.

"This means the world to him," Joe said.

In other City Title games:

* Wood 10, Franklin Towne 0: In AAA, at South Philly's Richie Ashburn Field, Larry Brittingham struck out seven while spinning a five-inning one-hitter. Jeff Courter (two-run single, first inning) and Mike Spahits (three-run triple, third) posted the big hits. Courter went 3-for-3 while Kyle McCrossen added two hits.

* Kennedy-Kenrick 11, Esperanza 1: In AA, also at Ashburn, Joe Harvey mowed down 10 in a five-inning stint while allowing four hits. Jimmy Volpe then struck out the side in the sixth and final frame. Dave Custer's three-run double highlighted a five-run fourth. AJ Koscelansky bagged two RBI on a fielder's choice and single. Esperanza led, 1-0, on Teofilo Bonilla's RBI double.