The latest experience of Sugar Ray Leonard conjures up a memory. It has to do with what used to be Time magazine's habitual, and later wearisome, lead-in for its obituary treatment of those deemed worthy of notice: "Death, as it must to all men, came last week to . . ."

Most certainly, Sugar Ray Leonard is not deceased, but if sad and bitter defeat and gory spectacle are substituted for the death factor, Time was paraphrasing the inevitable fate of aging, time-worn boxing champions who, as did Leonard, answered one gong too many.

It happened to all of them, scores of them, with two notable exceptions. Champions Gene Tunney and Rocky Marciano broke the mold, retired on top, never returned to the ring, and spared themselves and their admirers the last suffering, the final agony.

A word or two about Tunney and Marciano. Tunney reveled in what became his reputation as a Shakespearean scholar, which was spurious, and fancied himself above boxing, after beating Jack Dempsey twice. He also married into the Carnegie millions, taking Polly Lauder as his bride; he was of independent means anyway, having taken a $990,000 check as his end of the second Dempsey fight in 1927. 'Twas easy for him to quit the prize ring.

Marciano, by contrast, had no pretensions of scholarship. The stocky kid born into the Brockton, Mass., Italian ghetto always knew where he came from. He fought for a living, never caring much about the art itself. Yet he still compiled one of the greatest records boxing has ever known, 49-0. Forty-three knockouts. He was a terror in the ring, affectionate outside of it. He always fought bigger men and beat them all. When, at 46, he came to his death in the crash in Iowa of a single-engine, private plane in 1969, it was written here: "The failure must have been mechanical. Rocky's single-engine heart would never let him down."

One could weep at the memory of the end that came to so many champions. In his tries at getting one more payday, however meager, Sugar Ray Robinson, the finest boxer-puncher of all, stumbled about from city to city getting whipped by clods he once would have pulverized.

Who was greater than Muhammad Ali? At 38, he too was out merely for a needed payday, courtesy of his old sparring partner, Larry Holmes, who battered Ali for 11 rounds and pleaded with the referee to stop it in the name of mercy.

Joe Louis would leave a whole generation to grieve at his decision to return to the ring at 36 and lose to Ezzard Charles. And nine fights and a year later, what happened to Louis against Marciano was unforgettable in the saddest sense. Rocky dominated him, finally knocked him out of the ring, draped over the highest rope, where he was left in a ludicrous, pickwickian sprawl. For Joe Louis, a sight unimaginable. He was a favorite in that fight, signifying old memories.

Sugar Ray Leonard wasn't knocked out, but such an ending might have been less cruel than the battering he took from young Terry Norris. Much was made of the fact that Leonard could call on his native courage and last a full 12 rounds. But in the late rounds he was a feeble, groping, old champ.

As usual they said after the fight, "Ray's still got lots of heart." It drew from veteran trainer Gil Clancy the retort, "And that's the worst thing he can have at his age -- a heart and nothing else." Indeed, sometimes heart can be confused with common sense. When, against Leonard, Roberto Duran knew he was taking a bad beating and decided "No mas," he had decided to escape more brutal punishment. In British fight circles this sort of thing is regarded as "noble," the courage to admit that further fighting is useless.

When Leonard climbed into the ring against Norris he didn't look fit to his former trainer, Angelo Dundee. "He had no business in there at 154 pounds," Dundee said. "It was 10 years since he made that weight. He was walking around at 160, 165. You can take it off, but the muscle tone is gone and so is the speed and strength."

Also it could have been said that Leonard in all of his important fights had never before faced a counterpuncher, typified by Norris. Duran, Hagler, Hearns were all aggressive types with whom Leonard knew how to deal. Against tacticians like Norris, left-hook specialists like Leonard leave themselves open to the counterpunch. Left-hooker Norris, a counterpuncher by trade, loved it. When he had Norris in a bit of trouble a couple of times, Leonard, the superb finisher, couldn't finish him off. At 34, the swiftness, the clubhead speed was gone.

In all of the postfight babble the most fatuous statement was delivered by Mike Trainer, Leonard's well-intentioned attorney-manager, who said he knew as early as the fifth round that Leonard was done. "I wanted him to finish on his feet and go out right."

To go out right? To take seven more rounds of brutality while drained of speed and clout, bloodied of eye and lip and striving merely to survive as a punching bag for the new kid on the block? The courage was there, but the glory of it is debatable.