O'Neill has certainly taken to Mignolet.
"He is a very impressive young man and an intelligent boy," said the Sunderland boss.
"He has been fantastic, really fantastic and at this minute any accolades bestowed on him he really deserves. He is brave and the big thing he really wants to improve and he is as good a trainer as we have at the club.
"This boy is only 23 and he can improve by a big percentage even yet. He is gaining experience and there is no reason why he shouldn't be a really fine top quality keeper for a long time."