Manchester City first-team coach David Platt has praised Matija Nastasic for the speedy way the Serbian defender has acclimatised to English football, describing him as "an old head on young shoulders".
Nastasic, 19, arrived from Fiorentina on transfer deadline day in August and was given a debut in September's Champions League trip to Real Madrid.
He has gone on to displace Joleon Lescott from manager Roberto Mancini's first-choice XI, starting City's last five Premier League games.
The Premier League champions have kept three clean sheets in that time and Nastasic has looked increasingly at home.
"That is testament to him," Platt said. "He has stepped in. The first couple of games he has had to get used to English football but he has done that very quickly."
Former England captain Platt was particularly impressed by Nastasic's display in the 0-0 draw against West Ham earlier this month.
"The real, real good performance - he has had several good ones, but the real one where it might have been a bit alien to him - was when we went down to West Ham," Platt said.
"They were hitting the diagonal balls towards Andy Carroll and I thought he acquitted himself exceptionally well. You get that a lot in the Premier League that you don't get in Serie A and it shows there is an old head on young shoulders to adapt to that."
City have only conceded 10 goals in 13 league games this season and can boast the division's tightest defence.
"I think we have conceded fewer goals than at this stage of last season," Platt said. "But there's only really one statistic that counts and that's the points.
"You can draw comparisons to last season. We were setting records left, right and centre with how many goals we scored after 13 games last season. We would like to have a few more [this year] because it would have got those extra victories but 13 games gone, one point off the top, still unbeaten, there's enough in there to be pleased about."