Improve created players:
After creating a player in Career mode, every match you win will earn experience points. Disable the auto save feature. Once you reach Junior level you will start getting 50, 70, or 100 experience points per match. You can accrue the points of two or three tournaments and you can spend them in the player area. When you finish improving the desired areas, save the player improvements then exit Career mode without saving your career progress. When you play Career mode again, the tournaments you played to improve will be there to be played again, as well as the player improvements.
