Pulis has warned his rivals that he will now get even better.
He said: "We were looking for a young centre-half. I went and watched two games.
"We were very fortunate to get Sir Alex to say we could have him on loan and we did a deal where we could sign him.
"Everything that surrounded it was first class. He was very raw then but did exceptionally well. And he has got better.
"I watched him for 20 minutes and thought he could do what we wanted him to even though he was gangly and skinny.
"I still think because of his size he won't mature until he's 27 or 28.
"His best years will be in the next two or three years. He'll hit his peak when he's 27 or 28. He's still growing now!
"He's a lovely lad to work with. He's very dedicated with a lovely family, wife and couple of kiddies. He's very level headed and down to earth."