Sugar Ray Leonard loaded his flying fists with an impressive new authority today, knocked out Frankie Santore in the fifth round before 4,450 in the Civic Center, then took on what he described as his critics.

The gold medal winner in the Olympic Games won his fourth straight professional bout by knocking out the veteran of 32 bouts, knocking him down in the fourth round and then out after 2 minutes 55 seconds of the fifth with the second knockdown of that round.

In the interview room, Leonard took the microphone with the same poise he exhibited in the ring.

"It seems fun," he said. "First, the critics say I can't hit, that I'm just fast. Next, they'll say I can hit but I'm not fast. But I'm happy with the way the fight went."

He should have been. He was remarkably fast with his hands and there was evidence of the strength in his muscular arms in the second round when he hit Santore so hard with a 1-2 combination to the head that the Floridian's ankle gave way under him and he nearly went down.

Santore appeared as though he were trying to tackle Leonard in a frantic effort to clutch and hold the fleet-footed dancer. When Santore did catch up and clutched Leonard's arms, as in a vice, the stylist from Palmer Park, Md., flung him to the floor with the strength of his upper body.

Santore, who had an 11-bout winning streak ended by Leonard, did not make it to the interview roon and his manager reported he had, indeed, suffered an ankle injury.

Santore said of Leonard's hand speed, "He was exceptionally fast...I didn't think he was that quick."

By the fourth round, Leonard had Santore concentrating on self-preservation by bouncing bolo punches, right overhand leads, and numbing left hooks off his head. Once more Santore tried to tackle the elusive Leonard about the knees.

He made his biggest tactical mistake when he appeared to intentionally step on Leonard's foot to slow him down and the latter erupted in a flurry of rights to the head. Santore tied to tackle Leonard on the way to the knockdown, without success.

In the fifth round of Leonard's first scheduled eight-round bout, he raked Santore with so many head-snapping rights that Santore attempted a massive hug, but again was flung to the canvas. Then came a delibrately executed short right to the side of the jaw that decked Santoore.

That was followed by another savage series of rights that caused Santore to go face down. He nearly beat the count of 10, just five seconds before the bell!

Because Leonard had his opponent in serious trouble in the second round, he was asked afterward if he thought referee Tom Kelly should have stopped the bout in the third, when it appeared Santore had no chance to win.

"I wish they had stopped it in the first round, as soon as the bell rung," he said "But you can't tell when some guys are really hurt, even after they go down. You can't trust them; thay may be trying a trick. I think he was hurt in the second or third round."

Did he go into the fight with the intention of scoring a knockout, to silence the critics?

"No; you're going to get criticism no matter what you do. I did train for power. In Montreal for the Olympics I had to train for speed because my hands were hurt."

Manager Angelo Dundee alluded to the opponents Leonard has faced so far: "We said we would get better talent for Ray each time, but what the talent doesn't know is that Ray is getting better in every bout."

While the bout drew 4,450, Leonard was down for a percentage above his flat guarantee of $12,500. The crowd was not large enough to top that. Leonard also received $30,000 from ABC television.

Leo(Kid) Saenz, 162, of Potomac, Md., punched out a unanimous 10-round decision over Jimmy Savage, 163, of Philadelphia after suffering a cut right eye on a butt in the fifth round.

Saenz, who earlier drew with Savage in a bout at Capital Centre, was much sharper this time and was winning by a solid margin when he was cut, He still carried the fight to Savage after the butt. There were no knockdowns.

In a six-round bout, Wendell Bailey, 211 1/2, Baltimore, won a unanimous decision over Johnny Gause, 209 1/2, Philadelphia.

Charlie(Emperor) Harris, 217, Capitol Heights, Md., won on a technical knockput after 2:55 of the third round after Ira Martin, 215 3/4, Baltimore, suffered a cut. Referee Terry Moore stopped the bout.