The Magpies manager said "It's true that John has spent some time training with us.
"He has been very impressive as I'm sure you would imagine and from now, we have people talking to John and his agent, but I am sure a player of that quality will have lots of different opportunities available to him.
"So, we will see. We were fortunate enough to have him to come and train and look at what we are trying to do and how we are trying to work.
"Somebody with the talent and the career behind him that John has, for him to be able to come in and be completely comfortable within himself and with the players and staff, is really impressive.
"That was a very positive experience, we were really happy to have him and saw a lot of good qualities as you can expect but we have to see what happens with now."