Going with Ike Williams in his prime, in an upset. Williams, as Ltweight/ Jr. Welter, twice lost decisions to Kid Gavilan, a full-fledged Welterweight in 1949.
In here a lot aren't fully aware of him but he's rated highly by those that are. Our own Matt McGrain puts him #7. S.I. had him top 10. Boxingnewsonline had him #5 Ring didn't rate him in 1975 but then put him #5 in 1994 and 2001. To be honest i scoff at any top 10 list that doesn't feature him. He is almost always rated above Alexis at 135 (a great great fighter) and he would be favorite in this. His ko ratio is deceptive, he's one of the biggest bangers at 135 ever.