Looking at this trailer gets me winded. There's a reason I played fullback in my lone season of high school soccer - I didn't have to run past midfield. Hell, coach chose the goalie based on the fact he smoked.
Anyway, here's EA Sports Canada's Gary Paterson explaining how stamina and fatigue will work in FIFA 11, as they were variables that players didn't much understand in previous versions. Stamina is, of course, a player attribute that affects his ability to pull off those lung-bursting runs. Fatigue deals with how long he's been on the pitch.
That guy finishing last in the windsprints? That's me. I think you can see Dad in the parking lot yelling at me to get my ass in gear.