Xp, form and loyalty influence on a player

Experience

Experience simulates that an older player has managed to learn things not directly concerning his skills, which positively affects his actions on the field

Form

The better form a player is in, the better he will perform. It's not about the physical context though, it has nothing to do with how well trained a player is. Form in Hattrick reflects a combination of aspects making it possible for, or preventing a player, from reaching his full potential – like for example how his private situation in life is at the moment.

loyalty

Players with high loyalty to the club perform better on the pitch. Loyalty increases with time spent at the club.

Player skills
Keeper
Defending
Playmaking
Winger
Passing
Scoring
Set pieces
Xp.
Loyalty
Form