The World Cup winner cannot see why he would have wanted to leave previous club Schalke, who were a perfect fit for Sane.
"Sane will make several times his Schalke wages at Manchester City and that has been decisive in his decision to make the move to the Premier League," Matthaus wrote in his column for 'Sport Bild'.
"I cannot come up with any other reason. He was playing at a real traditional club at Schalke. I would have advised him to stay put for at least one more season".
As for being a success at his new club, Matthaus thinks life will be difficult for Sane at Guardiola's side.
"He will struggle at City," he added
"I do not have any doubts that he has the ability to enjoy a very successful career. He is fast, has great technique and does not seem to feel any pressure. He could have done that at Schalke where people were counting on him and challenging him".
Do you agree with Matthaus' comments?