Football players have become less mature over the last 10 years, according to Jose Mourinho, who believes they put themselves into bad surroundings.
Now at Manchester United hoping to lead the club back to the pinnacle of English and European football, Mourinho sees some key flaws in the attitudes of his players, insisting the kind of young professionals he worked with when he first turned up at Stamford Bridge in 2004 are just not there.
"I had to adapt to a new world. To what young players are now," he told France Football.
"I had to understand the difference between working with a boy like Frank Lampard, who, at the age of 23 was already a man, who thought football, work, professionalism, and the new boys who at the age of 23 are kids.
"Today I call them 'boys' not 'men'. Because I think that they are brats and that everything that surrounds them does not help them in their life nor in my work.
"I had to adjust to all that. Ten years ago, no player had a mobile phone in the dressing room. That is no longer the case.
"But you have to go with it because if you fight that, you are bringing about conflict and you put yourself in the stone age."
The 54-year-old says he has a better understanding of young players now and feels doing so is key to bringing out the best of them.
"If you stop a player from doing something, even something a little stupid on social media, you are going against nature," he added.
"I admit that having a son and a daughter at that sort of age has helped me to understand the way they function and what the world is today.
"I measured, from a methodological point of view, the nature of change. I worked as a result with my assistants to better, modify and adapt our work.
"Technology has given us new tools. Modernity and science too. But the key to everything, in terms of the leadership aspect, is to understand the people that you are working with today."