Have you seen the fight? It was pretty close. Duran was cutting off the ring well and (not seen it for a while so from memory but I'm pretty sure) that there was a KD that didnt get counted...
Dont particularly want to hijack this thread with a debate which has no answer. But, for what its worth, in my opinion there are two potential reasons that Duran quit; 1 - Coke 2 - He genuinely went nuts We're never gonna know why he quit. But I'd be deadly certain it wasnt because he thought Leonard could hurt him.
Not hurt him, a fighter like Duran would never worry about that... but maybe he didnt like the style that Leonard was applying that night, Roberto is at his best when a man stands in front of him, he had his most trouble with fighters that moved tho he was able to eventually catch up to them but this was at 135 (his best weight) & none of those guys (Bizzaro & Viruet) were in Leonards class. Then throw in the fact that he hated Leonard & Leonard took showboating to a whole new level in rd 7 & you might understand why he felt frustration. I will admit... its very unlike Duran to quit but the reasons for quiting I have described cannot be ruled out any more than any other.
The showboating maybe. I dont think Duran was particularly flumoxed by SRL's style though - well not to the extent to make him quit. Leonard had the flow of the fight but I think Duran would always be confident of finding him at some stage. It'll just be one of those things. To be discussed for years but never to be answered.