On Friday, Leicester's £17m centre-back is set to pick up his fourth England cap in the World Cup warm-up against Holland.
The former Sheffield United stopper said: “When I was playing in League One I used to analyse my opponents a lot.
“He was always a big handful – a good player. Then I thought he was a top player and he was going to be hard to mark.
“But then, I have progressed up the leagues and you come up against players who have played at the top level for years. Now it is Holland and Italy – it doesn't get any easier."