Dortmund CEO Hans-Joachim Watzke has claimed that his side are planning to keep Sancho at the club next season and the club extended his contract last year.
Manchester United have insisted that they are still interested in signing the winger, but they have been left frustrated by Dortmund’s negotiating tactics, including insisting on holding talks through an agent.
Dortmund want €120m and the two clubs have been working out on the structure of the deal that would take Sancho to Old Trafford.
The winger has travelled with the Dortmund squad for their pre-season camp in Switzerland and Hummels admits that there is absolutely no doubt about the youngster’s quality.
The Dortmund defender would be more than happy if Sancho decides to stay for one more season at the Westfalenstadion.
Hummels told German daily the Ruhr Nachrichten: “Everyone rates him positively. We do not have to argue that he is an outstanding footballer.
“He is still young, he can be a player who can make all the difference in many games and he has unlimited potential.
“If he wants to show that with us for one more year or more, I will, of course, be very happy.”
Sancho is Manchester United’s top summer target, but the jury is out on whether they can do the deal.