Warnock rates the Chelsea star the best left-back in the world.
"You realise what you've got to achieve trying to get to his level," he said. "It's a high level but you've always got to aspire to that.
"He's one that I always try and look at and try and improve my game.
"I think every left-back in the country will be watching him and seeing why he's the best. That's why people get better and improve all the time."