So for example, if I play fast tactics, and the player plays around 30-38 minutes per game, the higher the stamina, the higher his ranking and overall playing will be?
Not sure about rating being very different but certainly overall play will be better.
Because my team is great, but the stamina is low (1-4 skill), so training stamin for like half season straight could potentially be a very good idea?
Normally if I want to be competitive I'd aim for at least 5 ST, though I prefer as high as is practical.