What boxers come to mind when you think of talented boxers who had substandard stamina that was their biggest hindrance? First two that come to mind for me are: Zab Judah - Lightning reflexes and hand speed, but is usually a 4-6 round fighter. Cotto - 8 round fighter.
Zab's stamina isn't a problem it's his heart/mind. Pascal I always think his stamina is his down fall.
Zab Judah has victories over Cotto Mayweather Clottey If the fights were only 4 rounds of course Would have beaten Kosta Tzyu in another 4 rounder if not for Tszyu sensing the urgency of going down 2 rounds in a 4 round fight and getting Judah out of there
Stamina has a lot to do with patience. If a fighter is impatient or a knockout he will get tired early. If he relaxed he will have better stamina.
Jermain Taylor's poor stamina got him brutally KTFO against Froch and Abraham. Pre-Steward Wlad's biggest problem was his stamina, which led to some knockout defeats. Jean Pascal seems to gas and has to fight spoartically, which cost him dearly against Hopkins. Earnie Shavers was stopped quite a few times after badly hurting people earlier on due to punching himself out in 5 or 6 rounds.
Zab does lack heart, and is easily discouraged, no doubt. But his stamina is also pretty crappy, he is a notoriously good starter, but fades quickly as the fight goes on. He is much slower, and visibly tired as fights wear on.
Foreman of the 70's had pretty bad stamina too, but I hear he had some whacko trainer who dehydrated him for fights, only letting him eat ice chips the day before, and on the day of a fight O_O