1. Wladimir had the size, athleticism, and skill to give Ali trouble- bad style matchup for Ali.
2. Lennox and Riddick were both big men who had the jabs and ability to beat a prime Ali.
3. Larry Holmes in his prime gives Ali trouble with his jab.
4. Fury is a horrible match up for Ali.
5. Frazier and Ken Norton have Ali’s number and bad style match ups- they could pull the win out.

Ali is favored vs all of those listed, but I think they all are capable of pulling off the upset vs the great Ali.