What I'm getting this;
Everyone is aware that the PL and most especially United are bracing themselves for a big payout. Other clubs are alert and want a piece of the action via player sales. Benfica have a history of throwing the odd youth player in the squad to boost their transfer values, every one loves a young player breaking into the first team. Now add in the fact that this player is a Jorge Mendez client, you have hit the jackpot. You have to wonder why United arethe only club "genuinely" interested in him. Sanchez is like the fourth young Benfica player that has been hyped like this in recent months. From what I've seen from the guy, he is good but not this good. He was probably thrown into the first team because of injuries, or he was just better than the reserves (which doesn't mean much if the reserve side is nothing to write about) or just for transfer reasons. I know which it smells more like.
I'd rather focus on Pereira or spend that money on Alli