H-e-r-e's John (McEnroe, that is) in L.A.

Dear Boss: When you read this, I know exactly what you're going to say. Oh, no, not another one of those in-depth things on the behavior patterns of John McEnroe, the world's greatest tennis player! What has Peck's Bad Boy done now? Berated some linesman again, has he, for calling a ball in when it was obviously out?

Not to worry, Boss. I could no more analyze the five John McEnroes than I could characterize the culinary preferences of Konstantin Chernenko. Actually I think the hostility John sometimes generates between himself and spectators may stem from the Rasputin faces he constantly makes when he's playing a tough match. I mean all 751 of them belong in a scabbard.

But you should see McEnroe play tennis! Pete Rose in sneakers if you will. He jumps on every ball as though he's going for Pouncer of the Week honors. He's got so many shots he has to keep half of them on microfilm.

When the put-away is there, he's on the ball like a panther. Often his serves are just a blur. And when he returns service, his opponent had better be ready to run a country mile to track it down.

What brought this subject up, Boss, is that the other night I went to the Fabulous Forum in Los Angeles to watch McEnroe joust with Jimmy Connors in a hoked-up, best-of-three-sets exhibition. You won't believe this, but 15,853 other people had the same idea.

Hey, I don't blame the promoters for cashing in on this one. It was like taking Gary Hart campaign buttons -- well, from Gary Hart. But the promoters were very honest about it, not only billing it as an exhibition, but announcing that both players had been paid an equal performance fee beforehand.

McEnroe won 7-5, 6-3 in under two hours, the fourth consecutive time he has beaten Connors. It wasn't vintage Wimbledon-type tennis because the grass was a carpet and the ''sun'' had a lot of help from Thomas Edison. But it wasn't bad either, if you can distinguish entertainment from art.

Half of Hollywood was there, Boss, like Oscar-winner Jack Nicholson, Lloyd Bridges, Johnny Carson, Rod Stewart, Lionel Richie, and so forth. Even McEnroe was impressed, saying that he had never seen so many celebrities in person before at one time in his life.

Afterwards we all got together in a base drum of a locker room in the bowels of the Forum to ask questions and hopefully get answers. Everything was so low-key that I doubt if even Billy Martin, surrounded by marshmallow salesmen, could have gotten into trouble.

Honest, Boss, McEnroe handled himself in that press conference as though he was doing a TV commercial for a conscientious objectors' convention. You could hear the wings of the dove of peace fluttering in the background.

Know what McEnroe said? He said that Connors is a great tennis player who brings out the best in him. He also said that he hopes nobody ever comes to his matches to see him get mad because that's not what tennis is all about.

McEnroe really wants people to like him. He hopes anyone watching him for the first time will come away remembering only that he or she saw a great tennis player and not that other stuff. If Jack Nicholson had been in that room, I know he would have been tempted to consider John for the lead in a tennis version of ''The Reluctant Dragon.''

A couple of days before the McEnroe-Connors encounter, when I was doing research on both of them, I came across a quote in a national magazine where John's father said that his son was brought up having to fight for everything he ever got.

I later asked McEnroe what he thought his father meant by that? ''I don't know,'' John replied. ''Maybe it had something to do with the fact that as a kid I was just as aggressive in sports as I am now, and I played practically all of them. Or maybe my father remembers that I grew up complaining about my $5-a-week allowance.''

When someone asked Connors how much better McEnroe can become as a tennis player, Jimmy replied: ''John is like anyone else with championship talent. As great as he is, he can improve what he's already got by working harder.''

Oh, one more thing, Boss, McEnroe and Connors were both sporting fresh haircuts so short that in earlier years they would have been the envy of Mia Farrow.

Although there were reports that they collected $100,000 apiece for their two hours of fun and frolic, John told the writers present that it was less than that.

Know what, Boss, I believed him!

Foot-faultingly yours, Phil Elderkin