The midfielder has signed on a season-long with the Cottagers.
Hill said: "If Adel was right and was consistent, he would not be here, he would be playing for one of the top three or four teams in the world.
"Ability-wise he's one of the best players I have seen.
"It is just getting that consistency out of him. It's a big opportunity for him to go away to another Premier League team and prove to people that he does deserve to be there.
"If he gets that part of his lifestyle right and his mentality, then I am sure he can go on to be a player people will talk about."
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