Practicing certain areas of a player's game will help him improve his skills. See the following table for a general (not position specific) list of how each area may impact a player's game:
|Athleticism, Speed, Durability, Stamina
|Strength, Athleticism, Durability
|Elusivness, Athleticism, Speed
|Game Instinct, Technique
Generally, happy players (getting starts/playing time) will work harder during practice (work ethic improvements). With regards to the offenses and defenses, the more practice and playing time a player receives under each set, the better the offense will function in terms of efficiency.