Gareth Southgate: "I would rather not sell him but I know there are certain things we have to do as a football club.
"But Robert's approach is first class. Of course, it would be fantastic if he could go to the World Cup with Germany and a move might help him to do that.
"But he has been very realistic about it and has told me that he understands that for him to leave a club has to offer the type of money Middlesbrough want.
"Robert has the physical attributes for this division but he also has composure on the ball too.
"In addition, he has started to develop excellent leadership qualities. He has shown me his ability to be a leader over the summer and that's why I gave him the captaincy against United."