The loser in the first preliminary bout to the Sugar Ray Leonard-Roberto Duran fight tonight was rushed unconscious to a nearby hospital.

Cleveland Denny was knocked out by Canadian lightweight champion Gaetan Hart 20 seconds from the end of their scheduled 10-round bout by what Hart called "a right that made his eyes roll and then a left hook."

Denny was still unconscious more than an hour after the fight and a Maisonneuve Hospital spokesman said merely that he was being "treated."

A doctor who examined Denny, 24, of Lacshine, Quebec, and escorted him to an ambulance called the final blow "a tap" but said "he was unresponsive, his pupils were very sluggish, his pulse was poor."

"I've got to wonder about his physical condition, because he did not suffer a severe lash," added Carl St. Martin, an orthopedic surgeon from Newark, N.J., here as a spectator, who rushed to Denny's aid "because the ring doctor was very slow."

Dave Campanile, Denny's manager and trainer, said the former Canadian lightweight champion was in "perfect" condition and "conscious of everything" between the ninth and 10th rounds.

"It (the fight) was about even," Campanile said, "and before the last round he said: 'This round, I've got to go all out.' I don't think the referee let it go too long. The other guy doesn't hit hard. His (Denny's) last fight was in January, a draw in Los Angeles."

Denny works as a machinist between fights, Campanile said, and has a wife and seven-month-old son. His one loss in 18 previous fights was to Hart for the Canadian title in 1978. He beat Hart the first time they fought.

Ironically, Hart's most recent fight was a May 7 knockout of Ralph Racine, who required an eight-hour brain operation in the same hospital to which Denny was hustled. Of that ugly ending and tonight's, Hart, 26, said: "That's the name of the game. It could happen to me. I feel bad about it.

"My objective tonight was to win by knockout."

St. Martin said he was unable to remove Denny's mouthpiece before the fighter was placed in the ambulance, "but I really didn't try all that hard.

"I just happened to be here for the fight," he added, "I just came for the fight. The last blow was a tap. I don't think you can blame the referee (for not stopping the fight sooner)."

Earlier in the day, Hart had trouble making the required 135-pound weight limit. After running and other exercises, being wiped completely dry and stepping onto the scales naked, Hart made the weight. He immediately ate three ham sandwiches, a bag of pecans and a banana and drank two liters of orange juice. Then he turned to his handlers and said" "Okay, now let's get lunch."

In the semifinal, John Tate plummeted toward heavyweight oblivion when he was knocked out early in the ninth round by lightly regarded Trevor Berbick.

Ray Leonard's brother Roger earlier won a split decision over veteran Canadian lightweight Clyde Gray to remain undefeated.

Tate lost his WBA title flat on his face to Mike Weaver March 31 -- and ended in the same position after being pummeled by the Canadian heavyweight champion. Berbick hit Tate hard twice on the top of the head and Tate started across the ring.

Berbick caught Tate on the run with a left and right and sent him sprawling. Tate bounced and landed face down, as he had in the 15th round against Weaver.

"I hurt him with everything," Berbick said. "Everything. Rights and lefts. They might have looked slow, but they hurt. He called me a boy and that's the worst thing you can do. I wanted to whip him real bad after that." t

Gray said Leonard conceded defeat immediately after their uninspiring fight, but Roger later denied it.

"What do you expect him to say?" asked Gray, when Leonard joined him during a press conference and insisted his postfight remarks to Gray had been: "Good fight."

"I think I won it in the last three rounds," Leonard said.

"I always have bad decisions here," Gray moaned.