Jose Mourinho is "so intense" as a manager but most of his players would still speak fondly of him, according to Michael Ballack.
Ballack was signed by Mourinho at Chelsea in 2006 and worked under the current Tottenham boss until his first Stamford Bridge departure the following year.
The Portuguese coach's confrontational style has seen him clash with some high-profile players during a career that has also taken in stints at Real Madrid, Manchester United and Inter.
But Ballack feels Mourinho's charisma and ambition are attractive qualities and, despite his intensity, critical players are in the minority.
"You really get caught by his personality and by his ambitions," Ballack said to Sky Sports' Transfer Talk.
"Working with a coach like that was something totally new for me. He was impressive and I felt totally comfortable with the decision [to sign for Chelsea].
"The relationship is still good with him. You will not find many players who speak badly about him."
Of Mourinho's sudden Chelsea exit in September 2007, Ballack added: "I was experienced enough to understand.
"When you are not winning, the coach is more or less the weakest person in the team who can be replaced.
"He was in his fourth year. If you look at the average time a manager has to work in a club, it was quite a good time.
"The way he worked was so intense that maybe you come to a point where things are not working anymore. Even then, the fans know what he achieved at the club to take them back to that level."
Avram Grant took over from Mourinho and took the club to the Champions League final in Moscow, where they suffered a heart-breaking penalty shoot-out defeat to Manchester United.
"He never really had a chance. It is really difficult, after Jose Mourinho, to work at Chelsea," added Ballack.
"It could cause a problem for any manager because Mourinho had such a relationship with the players and the fans.
"Grant managed the team in a different way. A lot of players thought he would be weak, but he wasn't. He was really smart and intelligent."