Ballack played for Mourinho during his first spell at Stamford Bridge.
Ballack said: "Going back to a club where the fans love him, the club loves him but also English football loves him (could be good).
"He is special and brings this little bit extra off the pitch as well. That is part of football today.
"If you see his success in club football over the last few years, it is fantastic. From my point of view, I can say I really enjoyed working with him in the two years. He was really professional."