He said: "Toni is a player of incredible potential. He is a great force and is strikingly fast too.
"Even if he does things wrong from time to time, a player like Jerome Boateng did too when he was the same age.
"I am convinced that Toni is one of the talents that will go to the very top. There were many enquiries from top Premier League clubs when I was manager of Stuttgart.
"But for Toni, it's most important to get regular first team football. He needs to add more consistency to his game and needs to have more stability."
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