I have come to the conclusion that Professional is, sadly, the best difficulty to play the game in. The AI actually fouls you and gets yellow carded, their amazing dribbling skills found in higher difficulties doesn't come into play anymore. And you can actually attempt a challenge without them telephatically avoiding it or, in the worse of cases, change directions in their dribble only for you to earn a yellow card.
When I say "sadly", however, it is because their defending is worse than in later difficulties, at the expense of having a fair match, where both of the teams actually suck. In higher difficulties, the opposition AI gets better, yours doesn't, their stats boost, yours don't. Just an hour ago I decided to up the difficulty from Top Player to Super Star, only to concede three goals: two from placed shots from outside the box from a really crappy player, and a third goal following a corner that my teammates decided to conceded by not clearing the ball away from the sidelines, when it was the best option at the time. Instead, they deciding to turn around and face the opposition, losing the ball all the time.