Sugar Ray Leonard seems to have a chin as hard as Woody Hayes' head. In 17 professional fights, Leonard has not been knocked down. His people say he has been woozy only once.This is bad news for Johnny Gant, whose best shot for victory is a knockout.

Jim Croce did a song for a hero who moaned that he had contracted "the low-down, mind-messing, working-at-the-car-wash-blues." Our dripping hero claimed he was a Howard Hughes hidden by suds, and it was the world's misfortune that such a genius went undetected.

A sneakered mastodon running uphill with a refrigerator on his back becomes famous in television these days. Johnny Gant is stuck in the real world. He has risen to the top of his craft only to find anonymity. He has the low-down, mind-messing, don't-say Sugar-Ray-to-me blues.

Gant fights Leonard Thursday night at Capital Centre. The result will have repercussions throughout the welterweight division. A Leonard victory would be another sign the game's golden boy is on the rise and ready for a championship fight whenever he wants it. For Gant, victory is more important than that. A defeat may consign him to anonymity for ever. Leonard can lose and still sell Dr. Pepper on TV.

No one can say Gant's motivation will make a difference Thursday. Leonard has proven in 160 amateur and pro fights that he meets every challenge. With knuckles sore to the gentlest touch, he won a gold medal in the 1976 Olympics, a kid beating up the world's best amateurs daily. He has won his 17 pro bouts without a fight.

"This kid, thank God, keeps making a liar out of me," said Angelo Dundee, Leonard's manager. Whenever Dundee set up a bout for Leonard, the man who has worked with seven world champions said Sugar Ray was in for his "toughest fight yet."

Dundee is an honest fellow. He is infected with the bullfeathers fallout inevitable from working with Muhammad Ali 20 years, yet he tells the truth an astonishing amount of the time.So Dundee admitted to happy embarrassment each time Leonard took apart his "toughest" opponent.

At last, Leonard meets a considerable fighter. Whatever we make of motivation, it is a concrete fact that Johnny Gant can put some hurt on you. Of his 44 victories, 25 have come by knockout.

"He is a banger," Dundee said. "You ever hear of Baquedano?"

Is that a bean dip?

"Jose Baquedano was known as the dreadnought of the welterweights. Johnny Gant goes to Baquedano's backyard, Los Angeles, and knocks him out in the eighth."

That was Sept. 17, 1976, and chances are Gant did the damage with a right hand. Dundee was also Gant's manager until the Leonard fight was arranged (he has dissolved all contracts with Gant now). Trying to make a fight for Gant, Dundee once called a manager on the West Coast, who promptly said he didn't want his fighter in the same building with "that right-hand punchin' sucker."

At 29, Gant is seven years Leonard's senior. Leonard has been a pro less than two years, Gant 10 years. However "tough" Leonard's opponents have been -- some seemed eager to nap on the canvas -- the record shows that Gant has been tested by fire yet unfelt by the Sugar man.

Rushed in as a substitute with 11 days notice in 1975, Gant lost the decision in a championship fight with Angel Espada. He took out Baquedano and lost a 10-round decision to Esteban DeJesus, who once beat the terror Roberto Duran.

"I've fought 25 guys better than Leonard," Gant said yesterday.

A listener must have raised his eyebrow, because Gant looked over coolly and nodded confirmation. He did not smile.

Ali's dance with the past is forever intriguing. Every movement is invested with history and mythology. For pure boxing action, Gant-Leonard promises more than Ali has delivered in years. Two young men gifted with speed and courage will fill Capital Center with punches.

"Leonard's strengths in this fight are his quickness, youth, sharper reflexes and activity," Dundee said. "By activity, I mean fighting. He's had 17 fights in less than two years. (Gant has won six, lost one in that time.) That's how you get your education in boxing. You improve from fight to fight. Leonard's been going to school."

Now is the time for an examination. Because the fighters are local figures, Leonard-Gant has been talked of since the Olympics. Dundee was in no rush with Leonard. In making his early fights, Dundee said, "You look to stay away from maturity, you look to stay away from strength."

So they stayed away from Gant.

"Gant is a good puncher with quick combinations," Dundee said. "He punches you in close. Got that excellent right hand. He's a good pro. He could step in tomorrow against the world champions."

For Leonard, Gant is a step up toward the champions, Carlos Palomino and Jose Cuevas. Gant is not eager to take a nap at Leonard's feet. "It will be a great fight," Dundee said. Someone suggested that Leonard will make it great by connecting more often than the counterpunching Gant. How can Gant expect to win when he likely must win by a knockout? No one has ever knocked Leonard down.

"Ray hasn't been hit by a Johnny Gant," Dundee said. "I'm telling you Johnny Gant is a puncher. I'm sure Ray will win the fight. But I'll be scared every minute until it's over."