As Sugar Ray Leonard lies in a hospital after repairs to his left eye, it is hard to defend boxing, which is, after all, as ugly as a game can be when its object is to knock loose somebody's marbles. It also is hard to say that a year from now, with the eye fixed, Leonard ought to be cheered if he fights again.

These are not things many people want to hear, even respected fight people who have been, in the early voting, unanimous in deciding that Leonard ought to hang it up for good now.

If Ray Leonard fights again, I will be glad.

He is a bright young man, already a multimillionaire with world fame. He doesn't need to fight. It would be foolish to fight with one good eye, as some say Earnie Shavers does, for then it would not be Ray Leonard at work but only a pretender raging against fate. If the doctors and nature give Leonard's retina as firm a hold as it came with, why not fight?

There are quick answers why Leonard ought to retire from fighting: because he can be blinded, because he has more money than he can spend sensibly, because he has run out of challengers, because boxing is an animalistic exercise in sadism not worthy of Leonard's charm.

These answers make great good sense, but they fail to consider the most important reason Leonard fights. It is true that once upon a time he fought for money, so his father could quit work and rest his bad back, and so he could buy a house for his mother. True, he did want fame, but it was his soon enough and only two weeks ago he wished out loud for a moment alone.

Leonard could have quit fighting after Duran II if he fought only to keep his accountants busy while he polished his quips for Cosell and Carson.

Someone once asked Frank Shorter, the Olympic champion, why he punished his body through marathons. "Because I'm good at it," Shorter said.

No matter how often Leonard uses his Madison Avenue jargon--you'd think "marketable commodity" is his middle name--at bottom he is an athlete whose work in the arena makes him whole. He could have taken the money and run. Just last year, in training for the Hearns fight, Leonard noticed Muhammad Ali hanging around, the old champ seeking reflected attention. That is celebrity. Leonard needs more of this the way Cosell needs a thesaurus.

Leonard keeps fighting because he is good at it.

Because he loves the beastly game.

They couldn't get Ali to quit because, yes, he needed the money but, more important, because the old fire horse wouldn't admit he could no longer pull the wagon. Ali was honest only in the ring against a great fighter, and then he was a beautiful creature, as close to a living flame as God ever made. AliFrazier the first time was the Sistine Chapel of fights, a work of art that again proved this ugly game can raise a man to majesty thought beyond his skill and courage.

Ali couldn't let go of that.

Ali couldn't let his gift of talent go without using the last piece of it.

Jimmy Ellis, a former heavyweight champion, was thumbed in the left eye during a workout in 1975. He suffered a detached retina and never fought again.

"There's a difference between Ray and me," Ellis said yesterday. "I wasn't 25, I was 34, almost 35. And I wasn't at the top of my career, I was fighting for a payday by then. I had surgery but I never got good vision back, the way I hear Ray might. My only advice to him would be that he's young and at the heights now and the operation may be 100 percent--so just wait and see."

"I am terribly upset by this," said Ray Arcel, 83, a scholarly trainer so long in the game he can put Benny Leonard and Ray Leonard in the same sentence with authority. "I wrote Ray a note wishing him well."

Arcel, who trained Roberto Duran, spoke by telephone for 20 minutes. Every mention of Leonard was in the past tense. "Sugar Ray Leonard possessed natural ability in addition to mental energy . . . Sugar Ray was a great little fighter . . . " And finally Arcel said Leonard ought to quit.

"I sincerely hope he won't fight again," Arcel said. "He doesn't have to fight. How much more money does he need? He can do so many other things. Commercials, TV, movies, anything."

But what, someone asked, if Leonard simply likes to fight?

"I know he enjoys the excitement, the crowd. It gets into your blood like you wouldn't know if you haven't experienced it. But I know Ray has some very intelligent people with him. Janks Morton is a lovely man who has his heart and soul in Ray. He'll have a strong influence in keeping Ray out. Mike Trainer will, too. And the kid himself has enough common sense."

Common sense, Arcel said, means Leonard won't listen to any doctor who tells him he can fight. "I know too many fighters who tried it and went blind," Arcel said. "The gamble is not worth it."

Already, though, Trainer, Leonard's lawyer, is talking as if fighting again is a possibility. And if Leonard wants to fight, just as he wanted to beat the unbeatable Duran, as he knocked out the invincible Hearns, as this wonderful athlete has done a hundred things people told him he couldn't do--then, yes, we will stand and cheer when Leonard throws his next punch.