I was talking to a mate of mine the other day that is into body building big time, and I mentioned this subject to him.
He himself has gone off the HGH and partially the roids due to this thing called 'peptides' (no pun intended). He says he heals quicker, grows more, endure more, shed fat easily etc., basically all the ups of HGH minus the bones and organs growing. As he explained to me there are basically a peptide for everything, be it growth, endurance, strength, shedding fat, restituation etc.
He explained to me that these peptides are basically protein-chains combined a certain way, so they are extremely hard to detect. Also they are extremely short acting with zero half-life, so they just shoot up at very certain times like 30 minutes pre and post workout etc.
This might be what footballers are shooting up with.