He's only just turned 20 years old.
Gary is a massive talent who will come good. To expect the kid to come straight in when given a chance and make a difference at this level is a huge ask imo. Only a few players at that age can do that like Rooney, Oxlade-Chamberlain and Jack Wilshire, but your talking supreme talants.
Gary was watched by both Inter Milan and Real Madrid before he did his ACL, so that shows that the footballing world is fully aware of how good he could be and the potential he has.
He'll come good i have no doubt, just needs time to get upto speed. As Ulver said above, a good 6 month loan to a top end Championship team would do him the world of good.