Potter managed James last season with Swansea City and spoke of the winger before Sunday's defeat at Old Trafford.
He told The Argus: “I can see Dan's qualities there.
“His pace is incredible. Then his ability to reproduce that pace often is of such a high level.
“Then he has got that courage and resilience that people don't see so much.
“He gets kicked all over the place but gets back up again.
“He has had to deal with personal circumstance off the pitch which I am sure have challenged him and he has managed to settle into a club like Manchester United and play quite regularly.
“To move from the Championship to Manchester United is not to easy to do and I think he has done it really well."
Surprisingly well? Potter replied: “I think it is fair to say there is always that element of unknown when you take such a big step.
“But, when you know the person, Dan is an incredible lad.
“Such resilience, such personality, character. He does his work for the team.
“And then he has his own attributes which obviously attract Manchester United. I'm delighted for him."