You had to figure Sugar Ray Leonard would fight Marvin Hagler someday, because they are only 10 pounds apart, and what's a few pounds when there are millions of bucks to be made? So get out your calendar and write on September's page, "Sugar Ray dances with Hagler." Several Washington Post pugs beat this scoop out of Sugar Ray over chocolate mousse for lunch yesterday. He never laid a glove on us.

The idea, Leonard said, is to get Hagler right away. On May 14, Leonard defends his welterweight championship against Roger Stafford. Ten days later, Hagler dangles the middleweight title in front of Tommy Hearns. The Hagler-Hearns fight could be a bombs-away war, and so Leonard, giving Hearns only a small chance at victory, yesterday said he wants Hagler as soon as possible thereafter.

"The best time is right after a major fight," Leonard said. "That's why I went back with Roberto Duran in five months. We knew Duran was hurt in the first fight, and we figured I'd heal faster and he'd party hard for two months. Yeah, Hagler this September."

Anyway, now that Duran is back in Panama eating his way to blimpdom, a Hagler fight is Leonard's only megadollar possibility. However fearsome Duran once was, Marvin Hagler is the left-handed version. He is, for sure, Duran without the hair, having shaved his dome to induce fear. This shaving is redundant, kind of like putting a Nixon mask on Nixon, but if it makes Marvin happy, who's to argue?

So frightening is Hagler to middleweights that he has run out of body donors in his division, the latest volunteer one Caveman Lee who didn't last long enough to spell fire, let alone invent it. On May 24, Hagler gets a shot at Hearns, who once caused sleepless nights in the welterweight division but now appears to be no more than mildly annoying as a middleweight.

"Tommy hasn't done a thing," Leonard said yesterday. Such an assessment takes in only the latest part of Hearns' career, the two undistinguished fights he has made at 160 pounds instead of the 147 he carried while beating up on teeny-tiny welterweights.

"And Hagler is a monnnn-sterrr," Leonard said.

His eyes grew wide.

His breath grew short.

If you listened real hard, you could hear Marvin Hagler's footsteps coming splish-splash out of the swamp.

By the time Hagler is through with Hearns, Leonard figures he will have taken care of Stafford in Buffalo. Not only that, this most ambitious of champions--three fights a year the last two years--has plotted a schedule that includes both Jose (Pipino) Cuevas and Marvin Hagler.

"Cuevas after Stafford, probably in July or August," Leonard said, "and then Hagler."

Well, in 11 words Leonard said (1) he will beat the No. 3 welterweight contender, and then (2) will beat a former champion once considered invincible before (3) taking on a chrome-domed monnn-sterrr who hasn't lost a fight since who knows when.

Leonard said all this authoritatively, allowing no suggestion that anything could change his plans. He might have been an Amtrak conductor reading off the stops to Newark. This smacks of supreme self-confidence, but Leonard wraps his packages with such charm and orginality that only the hardest of cynics suspects the package contains the arrogance of, say, Muhammad Ali. Yet, like Ali, Leonard by his work has earned the privilege of counting his eggs in April when the first isn't to hatch until May 14.

The victory in Duran II followed by the late-fight technical knockout of Hearns not only certified Leonard's greatness in the ring, they were the beginnings of his obvious march into history. At the Montreal Olympics, Leonard said he wouldn't turn pro; as a pro, he thought of retiring quickly; but now, as rich as any man needs be, with no more victories necessary for any reason, Leonard keeps on fighting.

"For the history books?" one of our editor/pugs asked.

"That's what drives me," Leonard said. "You make history without realizing you're making history. That's when it's much more appreciated. I love this sport . . . I love the big fights, I love the challenge. I'm a competitive athlete."

However foolish his first fight with Duran was--he chose to get into a street fight with a guy who (cross my heart) keeps a pet lion in his backyard--Leonard redeemed his excellence with an artist's flourish in Duran II. He hit Duran at will. He eluded Duran's every punch. It wasn't 15 minutes into the job before Leonard was taunting Duran by windmilling with his right arm while delivering a jab.

"People say it's wrong for Ray to embarrass fighters," Leonard said. "I think it's smart. If I can embarrass a great fighter, I think that's a hell of an accomplishment."

Leonard laughed. "It's healthier, I'll tell you that."

In the first Duran fight, remember, Leonard thought to slug it out.

"A dumb fight?" said one of our pugs, perhaps the fellow who identified himself to Leonard as "a former University of Virginia intramural welterweight champion."

"I think it was an emotional fight," Leonard said. "I don't know what . . . "

He still can't explain it without stumbling over the words.

"It was something I wanted to do. I don't know how you want to phrase it. Macho? I mean, was it a matter of who was tougher? I reverted back to street tactics. Like, the toughest kid on the block. And Duran just happened to be in the street longer than I did."

Happily for Leonard, he grew very smart in the next five months and went back to his familiar style that so discombobulated Duran. We could go on about Duran II, but we're running out of space and you know most of it anyway. Come back Friday and we'll laugh a little as Leonard talks about the nervous moments before the Hearns fight. That, and Leonard on his Palmer Park roots.