Nadal bulked up and jumped straight into the seniors, hardly bothering with the ITF circuit. He never made it higher than 145 in the junior world rankings.
http://www.itftennis.com/juniors/players/player/profile.aspx?PlayerID=100007935
The significance of Roelant's comments about Nadal's physique being "100% ped" and his view that 20% of the pro circuit overall is on the juice, demonstrates the extent to which doping is accepted as part and parcel of the pro tour. It's routine, mundane, prosaic.
It will be interesting to see over the coming months whether Murray decides to use chemical assistance (or change his programme) to bridge the gap between himself and his rival Djokovic who has to be as near a certainty as those arch dopers, Nadal and Ferrer. Whatever he's on at the moment isn't working. His collapse against Djokovic was spectacular, a glorified tank almost. I think he was just fed up, wanted out of there once he realised that it was basically impossible to beat a fully-juiced Djokovic who was playing rope-a-dope with him.