Speaking to BBC Sports, Rangnick said: "We got to know each other back in 1998 when I became head coach of Ulm in the third division. At the time, I think Thomas was 25. Unfortunately, he had problems with his knee. What was obvious was that he was a very bright, intelligent kind of person for a football player.
"Being smart, bright, asking questions, always trying to get better, to improve. When you become a head coach, you can pretty precisely tell which player could become a coach. So when I found out he was working in a bar in Stuttgart, I called him and said to him 'What are you doing?', and he said, 'I have to earn my living there'.
"I said to him, 'Thomas, please, why don't you come to us to Stuttgart and work as a youth team coach?' We brought him together with the academy director at the time and that's how his coaching career started. For me, it was clear that he could become a very good coach. To foresee that he would become one of the best coaches we ever had, at that time, was difficult."