That is according to the Daily Telegraph's Matt Law who told Sky Sports' Sunday Supplement program that the Belgian has embarrassed his former club and old manager Jose Mourinho by becoming one of the Premier League's best players.
De Bruyne, 25, was not afforded the chance to prove himself under Mourinho at Chelsea after joining from Genk in 2012 and folllowing a loan with Werder Bremen was offloaded to Wolfsburg in 2014 before returning to England in fine form with City.
Law said: "It's a nightmare for Chelsea.
"He made eight appearances for Chelsea, not starts just appearances.
"It's an embarrassing situation for Chelsea but I think it does lay at Mourinho's door. It shows his flaw with young players and managing situations in that he couldn't manage the situation to a point where he could show De Bruyne that there could be a place for him in that team.
"Mourinho claims that he told the board he wanted to keep him and did not want to sell him, but the lad himself had decided he needed to play and that he wanted to go. He made it clear there was no stopping him.
"It must be awful for them watching what he's doing now and I just can't ever seeing Mourinho trusting to play a player like De Bruyne in the centre. He would now that he's proven but I don't think he would ever have trusted him as a kid to play in the centre in the role he really wanted to."