Sugar Ray Leonard won himself a new championship tonight and Thomas Hearns retained an old one. But in each case what they did with their fists seemed a mere warmup for the shots they took with their mouths when their fights were over.

Behind the hype and the witch doctors, this evening was arranged for one essential reason: to put Leonard and Hearns within shouting distance of one another.

It worked. Before the night was over, promoters of the Sept. 16 fight between the two had plenty of grist for their hype-mills.

Hearns started it by saying he would make Leonard quit the way Roberto Duran quit against Leonard last November in New Orleans. Leonard came right back and said Hearns didn't have a brain in his head, suggesting "Let's get Thomas Hearns out here and we'll have an informal conversation right now."

Mike Trainer, Leonard's lawyer, laughed at that one. Even Bob Arum, tonight's promoter who has been neatly cut out of Leonard-Hearns, could not help but laugh. Everyone knew that tonight was only round one of an exchange of words that will build consistently between now and Sept. 16, when the two finally settle everything with their fists.

If you're scoring, give round one in the verbal battle to Leonard.

He had a built-in advantage tonight -- a good fight. Hearns' opponent, Pablo Baez, simply did not belong in the same ring with him. He never landed a solid punch and the first time Hearns really connected, with a right, it was over. Baez slumping to the bottom rope at 2:10 of the fourth round.

Leonard's fight was truly of championship caliber, against a worthy opponent. It made Leonard look good and he knew it.

"I can't wait for Sept. 16," Leonard said when Hearns, inevitably, was mentioned. "When will I start training for him? Oh, maybe Sept. 15."

Laughs all around.

Leonard also drew laughs while retracting an earlier statement in which he had called Hearns, "a dummy."

"I didn't really mean that," he said. "That came from the street. . . He's a great fighter, he's destroyed everyone he's fought. He's got great physical assets, height, reach, great speed, great power . . . and no brains."

Leonard couldn't resist. After all, saying nice things about an opponent isn't going to sell a fight.

Hearns and his manager, Emanuel Steward, know that, too. "Baez is a good fighter," Steward said. "I know Thomas made this look easy, but that's what he does with all the men he fights; that's what he'll do with all the champions he fights."

"I'll fight him anywhere he wants," Hearns said."If he wants to fight in his hometown, Washington, thats fine with me. My only problem right now is that there's another man who is champion in my weight division. But that will change Sept. 16."

For now though, Leonard has two titles, Hearns one. And tonight, Leonard clearly had the crowd and fought the better fight. At least until Sept. 16 he will remain, as Hearns' press agent Jackie Kallen put it before the fights, "America's Sweetheart."

Perhaps the exits of the two fighters tonight summed up where they rate in the boxing world. Seconds after he finished his postfight press conference, Leonard and his bodyguards jumped into a huge black limousine and drove out a rear door of the Astrodome.

Ten minutes later Hearns and his group, who had gone to a private box to watch the Leonard fight, also left. They did so by walking from one end of the Astrodome to the other, then getting into their car.

The two men had one thing in common though. Neither had a mark on him. This night was as much for verbal jabs as fisticuffs. Maybe more.