Once you have created your player and started playing 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.
Play as Nadal
To get Nadal as a playable character you must first at the title screen with Roger Federer, hit 1, A, 2, Z, B, B, 2. Next at the players screen Hold down Z and Nadal's character box will appear below townsend. Where you hold Z matters, it must be on the Federer box.
Unlimited experience points
1.) First you need to create a player
2.) Earn some EXP points and spend on your skills in Career, Online or Tournament mode.
3.) Enter to the "Player Area" menu
4.) Choose the "Player Evolution" option.
5.) Select a skill by highlighting any skill option and pressing X.
6.) Spend your EXP points and press X.
7.) Now press X again and remove the experience points you just spent.
8.) Now press Circle.
9.) The selected skill will still have the points you spent, but they can now be used again.
10.) Repeat the process to max out all skills of your player.