Press Start at the main menu, then hold every other button at the same time. A new screen will appear, where you can select the team and then the player that you wish to have his name changed.
Cheat Mode
During the bounce up during a game, hold Up + Select + X then release Select, Up, X (in that order). Replace X with Triangle, Circle, or Square for different cheats.
Easy wins
Select Brisbane at the Gabba against any other team under the easy difficulty setting and you will be unbeatable.
Reserves
If a player has retired during the last season, there are 10 or more reserves you can put in to replace the retired players(s).