Ballack said: "I got a lot of criticism in the first months. But I know I am a good player. You don't become bad overnight. I was focused and dealt with the criticism. I had to learn to play with Chelsea. The year was getting better for me. I had some good games then I got injured and had to start again."
He said: "Eight months is a long time. I know some players who were out for over a year and that went through my mind. It was frustrating and difficult not to make big steps forward after six months."
Now the German is keen to show Blues fans why he made the switch from Bayern Munich - and what he can add to the talented squad.
He said: "I want to show in the next weeks and months why Chelsea bought me. It is not easy if you change country. It is not an excuse. I am happy with my play. In the first year, Chelsea had a different style of play.
"In Munich I was the main player. Here we have a lot of big players so my style and the way of playing changed a little bit.
"Chelsea won the title twice and you have to adapt. Every player needs time. You want to prove yourself. I see also that it is getting more difficult because we have a lot of good players."