Sugar Ray Leonard, who has been fighting for 10 years, may have thrown a million punches in his life. But he never threw one like his final left hook last night.

Leonard retained his WBC welterweight title at Capital Centre by knocking England's David Green unconscious at 2:27 of the fourth round with a blow so sudden and frightening that it should permanently answer all questions about the 23-year-old champion's power.

Green was rendered so stiff by that hook to his right temple, and lay so motionless, that referee Arthur Mercante ruled that it was "too dangerous to continue the count" and did not even bother to get to "10." Mercante stopped at six and hurriedly hailed the medics.

"He was going to be out a long time," said Mercante. "I was worried about more than the count."

So was Leonard. "That was the first time I was ever frightened by a punch I threw," said the ecstatic Leonard, now 27-0 after his first title defense. "It was the hardest single blow I ever threw.

"He laid so still that I'm just glad he's okay and came to in a few minutes," said Leonard, still bubbling with about 10 rounds worth of excess energy.

"That punch . . . well, everything about it was just on time. It was short, from the body and it hit him flush. It had everything in it. When he lay there and they checked his eyes, I had a strange and sensitive feeling. h

"Why sensitive? Because I don't really hold any animosity toward him."

That, however, was not entirely true. Green made a huge mistake last night. More than any other pro fighter who has faced Leonard, Green tried to psych, intimidate and sneer at the champion before the fight.

Green came out in a huge, perhaps ludicrous tiger-skin robe that made him look more like an Eskimo than an Englishman. After working up a lather by dancing around in the hot thing, Green began trying to bully Leonard by getting in his face, bumping him and snorting.

Some say Leonard lacks the killer instinct because he is too smart, too nice, too sensitive. But it isn't smart to try and show up the champ in the champ's home town. Green paid a cruel price throughout the fight as Leonard clubbed to the head with hooks from both hands in every round.

And after each round, Leonard glared at Green and gave him an "I'll-tear-your-head-off" look that he has seldom shown.

"People say I can't punch," said a smiling Leonard, who dropped Green's record to 33-3, all his losses by knockouts. "I still don't believe they're right.

"When are they going to realize that speed dominates experience? Speed dominates power. Speed dominates everything. Speed will always do the job." d

And perhaps no one in boxing, relative to his weight class, has Leonard's speed.

"I dominated Green mentally before the fight ever began," said Leonard, who after initally being surprised at Green's bravado, used his two-inch superiority in height to get nose to nose with Green and glare down at him.

"That's something I learned from (Wilfred) Benitez in my last fight (for the WBC title). I tried to do to Green what Benitez did to me. That night I couldn't do what I wanted to do. I was intimidated by the pressures and expectations of the fight for the first time in my career.

"Now, I'm relaxed. I'm the champ.Now people are going to see the real Sugar Ray Leonard. It started tonight."

While Green was being revived (which took several minutes), Leonard's entourage was celebrating. It was the second strong victory for the Leonard family tonight as brother Roger Leonard scored a unanimous eight-round decision over quality veteran Johnny Gant of the District. That win earlier in the evening may establish Roger Leonard as a possible junior middleweight contender.

Ray Leonard's evening was marred, however, just moments after the fight.As the Leonard camp was moving back to the Centre's subterranean dressing rooms, corner man Angelo Dundee was involved in an argument and was knocked unconscious. A hanger-on around the Leonard camp named Joe (Pepe) Saunders who fights under the name Pepe Corea, was held under lock and key by security guards. Dundee was treated for a mild concussion, the same diagnosis made on Green.

Leonard, who had not learned of the Dundee incident, was as jubilant as a man who had just earned about $1.4 million.

"Green was gutty. His blows had force. But he never really hit me. I think it got next to him when he realized that his best punches weren't touching me.

"I felt in control all the way. I dictated the pace. You defeat aggression by surrounding it, coming at it from all directions. I moved laterally constantly to keep him awkward."

Against a faster and better man than the game Green, the No. 10 WBC contender, some of Leonard's strategy might have led to danger. Leonard seldom used his peppering jab -- except once in the first round when a lightning jab gave David (Type-O) Green a slight nosebleed.

Instead, when Leonard stopped stalking or dancing, he thundered Green's guard -- then went for the home run punch.

The final sequence began the same way, with two hooks -- one left, one right -- whacking Green in the sides.

"Then it was a right uppercut and that last hook," said Leonard. "They both landed, but I've never had one like that last hook . . . not even in all the one-punch knockouts I had as an amateur.

"It was like hitting the heavy bag. Only when you hit the heavy bag, you don't win anything. Tonight I did."

Leonard's only disappointment may have been that the Centre crowd was estimated at 12,000 in a 19,500-seat arena where tickets were scaled from $10-$100.

"Why should that bother me?" asked Leonard, changing moods. "You know, not everybody in this town has money."

If Green's initial snarling act were not enough to waken Leonard, then the champ was roused when he saw WBA heavyweight champ John Tate cold cocked by Mike Weaver just moments before his fight. The crowd marveled at the violence on Telscreen.

"I saw it. It really made me think," said Leonard. "It's so hard to work your way up to the title and so easy to lose it. Seeing that knockout helped me."

Seldom has Leonard managed a more confident fight -- especially considering the 26-year-old Green's solid record, his top condition, and his credible 11-round defeat at the hands of Carlos Palomino in another WBC championship fight two years ago.

"I danced and confused him for two rounds," said Leonard. "Then I started to back him up, and look for the end."

When asked, inevitably, about plans for his next fight and the pressure being put on him to meet Don King's man Roberto Duran, Leonard snapped, "King is totally irrevelant. I don't feel any heat from him whatsoever.

"But I would like to fight Duran," said Leonard, who may be the first man ever to say such a thing and mean it.

What would happen if he met the man with the hands of stone and the 66-1 record.

"Isn't it obvious?" said Leonard, appealing to the clear evidence from last night's proceedings. "I would knock Duran out."

Green could not be reached for comment.

Presumably, he agreed.