It was supposed to have been changed to be based upon ratings and not necessarily individual performance as many teams can hold back players or they have the depth where they don't need to lean on a superstar.
However, the deeper that your team advances in the tourney, the more likely you will lose players to the draft.
Of course, there can be exceptions where u get knocked out in the first round and still lose several players and sometimes you can make it to the Final 4 and have a stud come back.
I don't think there is a hard rule, but it is more likely that you will lose players if you have a deep NT run.