Manchester City manager Pep Guardiola hailed John Stones, but hopes the defender is ready to continue improving.
Stones, 23, has developed into a key player for City, who are eight points clear atop the Premier League ahead of visiting Leicester City Saturday.
Guardiola said the centre-back just needed time to settle at the club after joining from Everton for a reported £47.5million in August last year.
"We cannot forget that last season was the first time he was able to play three games a week. Everton, they play once a week. Here, you have the Champions League. You need a process to settle," he told a news conference.
"He became a father and that helped his life to be well-organised. He has this amazing quality to understand the game, to be calm, to read the next pass.
"Defensively all the team helped a lot but he joined a good partnership with Nico [Otamendi]. Every game last season he made one or two mistakes and this season that is more irregular.
"He's still young and it depends on him if he wants to become better. Hopefully he still has the desire to improve because there are many things to improve with and without the ball."
Stones played 90 minutes in both of England's friendlies this month as Gareth Southgate's men held Germany and Brazil to 0-0 draws.
Guardiola believes Stones' experience so far with City, including in the Champions League, has been behind his improvement.
"He is more mature. Every player when he's 20 or 21 is completely different to when he is 27 or 28," he said.
"To have experience in the Champions League you need to live that. Last season in Camp Nou [against Barcelona], this in San Paolo [against Napoli].
"Then against the best in Neymar and Gabriel [Jesus] against Brazil. You need to live that to become a better player.
"You have a lot of skills and talent when you buy them but they have to live the situation to realise, 'OK, I can handle it'. For that, you need time. In football, you don't get time but you need it."