The 49-year-old, who is now sporting director at the club, has commended the performances of the Germany international and also spoke about the difficulties facing them in this season's Champions League.
“I said before the season started that we would see the best of Mario,” he told Bild. “It was just a matter of time.
“It is up to the coach where he plays, but Mario has the good fortune that he is as good in any position. He can play on the right, left, or play through the middle.
“We are German champions, so we of course want to go through. But it doesn't help now that we have Real Madrid and Manchester City. We need to make a good start and beat Ajax at home.”
The Dortmund-born ex-captain concluded the interview by stating he is extremely happy with the team's squad, despite the departure of Shinji Kagawa to Manchester United.
“I am absolutely happy with our squad. When I see Rafael Van der Vaart and Ibrahim Afellay join Schalke, I am of course a bit jealous. But we have attacking midfielders, and we saw no need to add to the squad," he added.