The 27-year-old was made the most expensive defender in history when joining the Citizens from Tottenham Hotspur in a £53m deal during the summer.
Stones believes that his fellow Englishman has more than lived up to the hype at the Etihad Stadium so far, having bagged four assists already from his first nine Premier League and European outings for the club.
"The way he gets up and down the pitch is why for me he's probably the best in the world, and I keep telling him that," he told reporters. "He wants to keep winning, keep on keeping clean sheets and getting better.
"That's why he's the player he is and the person he is, he wants to keep on getting better. I think it's down to the team, if he's so high there is always back to cover his position. It's down to the manager and players to ensure that happens and at the moment it all gels quite well together."
City boast the second-meanest defensive record in the English top flight, conceding just four goals in their first eight games - two more than Manchester United over the same length of time.