BVB chief Michael Zorc is adamant Sancho is now not for sale.
Hummels said, "Everyone is happy about it. We do not need to discuss whether he is an excellent football player.
"Jadon is still young, but he can make the difference for us. His potential is limitless.
"If he continues to deliver, as he has done until now, for a year or more, I would be really happy about it."