The youngster looked below his best at Villa Park.
He said: "Alex has not played a lot recently. He lacks a bit of physical fitness. He tried at Villa and in patches he looked dangerous.
"He's learning his trade and he's a very talented young boy. I believe he will be a great player but at the moment he is learning his job.
"Basically, he's 19 years old and there will be ups and downs, of course, but I believe he will be a great player.
"You need patience with every young player or you don't bring them out (see their potential fulfilled).
"That's why it's so different in our job where you see the demands of people who want you to bring young players out but also they have no patience so it's a bit of a contradiction."