And Zola believes Barkley has to be considered as a top midfielder.
"He had a big injury that stopped him from playing at his best in the last few years. That's something that has to be said.
"It's been important for him the way we play because it's making him a little bit more complete.
"We always knew he had ability - physical ability, technical ability. But to play the midfield position, he was lacking a little bit of tactical awareness and defensive awareness.
"He's doing very well right now and it's making him a better player. All these things, added to what he already had, is making him one of the best midfielders in the country."