Der Spiegel has a great article on how Jose Mourinho strips away your ego as a player and makes you into a machine performing for Chelsea. It is in German, so I'll give you the broad talking points.
This is Michael Ballack's transformation from preening German superstar to just another player doing Mourinho's bidding.
In the article Ballack has been reported to be in reverence of Chelsea owner, Roman Abramovich and coach Jose Mourinho. In Germany, Ballack was always pegged as somewhat aloof and a player who was respectful of authority. Probably befitting his East German upbringing. However, the more familiar he got with the system in the Bundesliga, the more he realized that there were too many preening coaches and vain players. Most Germans believed that greed played a big part in Ballacks transfer, as Uli Hoeness put it bluntly, but Ballack is too intelligent a player and realized that the Bundesliga had its limitations. Mourinho also seems to have struck a chord in Ballack in their meetings before his signing on.
Ballack is also very acutely aware of why he has been brought on to Chelsea. Not to win the Premiership. Been there, done that. Jose Mourinho is gunning for the Champions League. Mourinho is a martinet. Ballack can no longer wear his hair long. As with every Chelsea player, he now sports close cropped hair. He says of his transformation (only about a month long but then it only puts Mourinho's forceful personality in context), that he no longer looks in the mirror like other German players and is ready to play football.
The article also pits Mourinho and Abramovich as soulmates. Both having fought authoritarian regimes. Mourinho loves his role as a coach, comparing himself gleefully with Don Corleone, the Mafia boss from the Hollywood film "The Godfather", and he calls his squad "the family." An aspect that Ballack learned when Drogba scored that great second goal against Blackburn. There were no overt celebrations. Drogba had fulfilled Mourinho's duty, and that was the only thing required.