I'm not sure. As you might know, there is a hidden trait of aggressiveness in players. Some have it higher than others, which leads to higher fouling rates. Even if their defense is trained up to the level of competition, they still foul. I have heard that players with higher aggressiveness not only commit more fouls, but also draw more fouls. I'm not sure if this is true either. Your best bet would be to make sure that no player that's on your team or that you buy doesn't have a high fouling rate.