the "jamacan sensation" was certainly a great fighter, perhaps one of the most underated of all times. He would definitely prove to be a worthy opponent but I just feel that leonard would be a little too swift for him. It was speedy boxers that troubled mike the most and leonard was one of the speediest and best that there ever was.
I base my opinion mainly on McCallum's fight with Curry, but think Leonard would last the distance. Curry was exposing the one area McCallum can be outmatched, speed, before being knocked out. Leonard too fast and by decision.
close fight leonard takes a tuff 15 round decision as said to quick although mccallum's great body attack slow's leonard down in the later part of the fight but leonard holds on to sneak it