Grayson, a former Villa defender, was impressed by ex-Leeds United starlet Milner in South Africa.
"I think James has done really well," he told Villa's website. "He is a fantastic talent and everyone you speak to here saw what a talent he was when he was breaking through the youth team, reserves and then up into the first team.
"They said what a top pro he is. He works his socks off on the training ground - first in and last away. He is only going to get better.
"He's played in various positions and he has contributed and been one of the better players for England.
"He will only get better from the experience of being in a World Cup."