Zlatan Ibrahimovic and José Mourinho spent one season working together at Inter Milan, winning Serie A in 08-09.
The two will be matched in the Champions League with Paris Saint-Germain and Chelsea respectively.
Ibrahimovic had an infamous falling out with Pep Guardiola at Barcelona, which Mourinho doesn't understand.
“Easy, easy. I don’t understand when people say he is a difficult guy to work with or a difficult personality.
“A difficult personality [is] when you have to work with people who don’t want to win or don’t want to improve. When you have somebody that is a winner and wants to win all the time and wants to be the best and is not afraid of the big responsibilities, I think he is very, very easy.
“I only coached him for a year but it was a good year, a good experience and I rate him as one of the best players I have ever coached.”