What most people think, is that only the 14 highest players count for the draw, because that the minimal of players that you can have in the squad.
But nobody knows for sure.

If this is correct Buying weaker players will not help you, what some people do is not atribute he SP gained, that way your players we be weaker then they really are, only atribute those SP at the beggining of season.
But also nobody can be sure.