I don't understand why I have a player with 7 stamina has only 70% energy(lowest on roster) and other players with 1 in stamina are in the 80's while playing the same amount of time and they all only play on one side of the ball (offense or defense).

Don't much make sense to me.

Gurudefence wrote: The fitness levels is in regard to training! Not matches Stamina is believed to help the player achieve his rating in a given position during a match. It does not help with training! Hope this helps. Guru. EDIT: Training was last night

Excactly.
Stanima will help your player keep his rating up throughout games.