You are excercising your body for 90 minutes at a high stress level, so stamina is needed to achieve this.
So you can play the whole game if you don't have good stamina they don't put you in the whole game
Stamina is important because you need to run for 90 minutes and still compete for the ball, but you can’t compete for the ball if you haven’t got any energy.
Just start drinking water and eat fruit