Chelsea scout Piet de Visser admits he was angry with both the club and former manager Jose Mourinho for allowing Kevin de Bruyne to leave Stamford Bridge.
De Bruyne, 24, was frozen out of the Blues first-team squad upon Mourinho's return for a second spell in charge in 2013, making just three Premier League appearances before signing for Wolfsburg in January 2014.
Back in Germany the Belgium international flourished, transforming into one of the Bundesliga's hottest talents before returning to these shores last summer when Manchester City made him their club record signing for £55m ($79.7m).
His rise has continued seamlessly at the Etihad, something that has come as no surprise to De Visser, who warned Chelsea De Bruyne was ideally suited for English football.
"I was angry with Mourinho when De Bruyne left Chelsea," De Visser told Belgian newspaper HLT, the Daily Mail reports. "We talked about it. Then he would say, 'Piet, I find it a shame too, but the boy wants to leave. He doesn't want to train under me any more.
"I told him: 'Yes, the boy wants to play. He is ready for it.' I tried to convince him on Kevin's qualities, but then Mourinho repeated: 'Piet, he doesn't want to train.' I went to see a training session, Kevin was the best player on the pitch."
De Visser added Mourinho believed De Bruyne would not be ready for a first-team role for another two years, something both he and de Bruyne disagreed with.
"Look, Mourinho is a performance-focused manager, who has achieved a lot in his career. He wants to work with fully developed players. He thought Kevin needed one, maybe two years. But Kevin was ready. And Kevin was convinced he was ready too."
De Bruyne immediately became a crucial member of City's starting XI following his return to the starting XI last summer and has scored 16 goals and laid on a further nine in all competitions this season.