The Welshman, now boss of Greek side AEL 1964, told the People: "You're walking into a dressing room full of egos at Chelsea, even more so than at Fulham. Every one of those players is famous the world over and for a guy of 32 or 33 that could be intimidating.
"He'll need to earn respect immediately. Players will be thinking: 'What's this guy going to do for me? What has he achieved? Is he going to win us the Champions League?'
"So you have to have a certain arrogance and inner belief to manage in the Premier League at that age. You're the most important man in a multi-million pound business.
"Even though you have a chief executive who will take care of most of the money matters, the business depends on you getting results - and you are accountable.
"The age issue is a double-edged sword. Because he's not had loads of experience, the players will be asking: 'What's he got that the last bloke didn't have?' Carlo Ancelotti has won the Champions League as a player and a manager, and he won the double with Chelsea, but still got the sack.
"In terms of man-management, though, it can help you relate to your players when you're the same age as many of them. But they have to know you're the boss - any ideas about being liked and being a nice guy have to go straight out of the window."