Kevin De Bruyne is reportedly ruffling feathers at Napoli and could spell trouble for Scott McTominay.
The Belgian's arrival has apparently caused a 'rift' in Antonio Conte's team because the entire system has been adapted to suit him - but only to mixed effect.
And his raging response to being substituted in the 2-1 defeat at AC Milan on Sunday, despite scoring, has raised a key question: is McTominay's sacrifice worth it?
There is no doubting De Bruyne's timeless quality. As he intended, the 34-year-old is showing Manchester City that are missing out - already he has scored three goals, including a free-kick on his debut against Sassuolo.
Napoli have won four of their five Serie A games with him and sit second in the league, hardly a disaster.
But he has forced Scott McTominay, last season's Serie A player of the year, out onto the left wing, limiting his effectiveness.
Kevin De Bruyne's arrival at Napoli has reportedly caused a problem - it has squeezed out Scott McTominay
McTominay has been forced to play on the unfamiliar left wing, limiting his effectiveness
But after De Bruyne's tantrum at the weekend, and his mixed form, people are questioning whether the sacrifice of changing the system for him is worth it
Marauding from central midfield, the Scot managed 13 goals and six assists last season. This campaign he has been limited to one apiece.
Significantly, Conte has switched from a title-winning 4-3-3 to an unfamiliar 4-1-4-1 to try and accommodate all of his 'Fab Four': De Bruyne, McTominay, Stanislav Lobotka, and Frank Anguissa.
But with two of De Bruyne's goals being penalties, and with the Premier League legend having provided no assists, he is coming under scrutiny.
As Italian outlet Sportsmediaset put it: 'Despite the three goals scored, De Bruyne hasn't exactly brought out the best in the team's play and, in fact, has forced Antonio Conte to change the balance by, for example, moving McTominay wide on the left into a position on the pitch that limits his effectiveness in front of goal.
'Mending the rift with De Bruyne, an exemplary professional who will likely quickly forget what happened, is absolutely essential. If only because the former City player, a key figure in Napoli's transfer window, should have guaranteed the Italian champions the leap in quality needed to repeat their success in the league and play a leading role in the Champions League.'
Journalist Eleonora Trotta told Calcio Mercato: 'After the praises for De Bruyne in the Champions League in Manchester, everything changed.
'There’s an issue. Both due to the substitution and the controversy, and because of his impact. His entry negatively affected last year’s championship factor, Scott McTominay.'
His tantrum at the weekend does not help his case. As Conte insisted: 'I hope De Bruyne was upset about the substitution because of the result, because otherwise he's got the wrong guy.
Antonio Conte says that the new system can lead to 'absurd excesses' and less control
'I tried to bring in fresh players for one-on-one situations, given that Milan were closing down a lot. I replaced Hojlund with Lucca. There's not much to say, I think the substitutions were the right ones.'
In the build-up to their Champions League clash with Sporting CP, Conte gave some puzzling comments about De Bruyne.
'If the team does well, he's fine, otherwise both of them do badly. He's someone who needs support,' he said.
'We're trying to find the right balance because it can lead to absurd excesses: if we win, it's fantastic; if we lose, it's all wrong.
'I need to have balance, look for the best solutions, knowing that this is the second year, and it will be complex for us, because we have to play every three days and bring in nine new players.'