Welbeck is currently on a season-long loan deal with the the Black Cats from Manchester United.
Welbeck scored a brace in the 2-2 draw with Everton.
“That’s the problem you have to face. If we can concentrate on the first bit and he can be exceptional for us this year and score 15 goals, we will deal with the other bit when it comes,” said Black.
“But first and foremost, we need to have the problem.”
“He is an exceptionally good player. I see him every day in training and he has got fantastic ability,” said Black.
“He has now got the confidence. Probably what has stunted his development is he has not been able to play regular football week in, week out.
“He is now getting that opportunity and he has grasped it. He has got phenomenal potential – that’s probably why he is at one of the biggest clubs in the world.
“But hopefully he is flourishing here and hopefully we can hang on to him for as long as possible.”