There are 2 main methods, it depends on the player's personality and his love to the club which method is more effective:
1. Kiss his *** (Give him all type of praise on and off the pitch, in press conference, private chat, hire staffs and players he recommends, set his status to key player, play him regularly, get rid of those he dislikes).
2. Kick his *** ( Warn transfer list, transfer-listing him with ridiculous price so no club could be stupid enough to make an offer, stop playing him, move him to reserve for his attitude, fine wage, complain if he has poor form, set his status to not needed or back up ). If it works, he will apologize after 4-5 match being bench warmer, or he will: "I'm concern that I'm not in your first team plan". You should: "I'm prepare to give you first team but I expect you to work hard to stay". This method is more effective with home-grown player.