Corruption is worse than almost anything in this world. I believe that the hunger of money can make any player sell their conscience and play for the people who bought it just because they've bet something big against the odds and want to win it at any cost. There's probably nothing that could move out the greed of a person than his own will not to commit such a thing.
of course, there are still people that know the importance of dignity and credibility. but there will always be individuals or group that will practice illegal stuffs for the sake of money. it may not be all, but there will always be someone who will corrupt the system one way or another.
if you want to live with clear conscience, it is up to you how you will live your life, whether you are an athlete or the coach.