Poland goalkeeping coach Andrzej Dawidziuk said: "Celtic obviously believe Artur is one of the best goalkeepers in the world.
"That's why they have kept their faith with him this season, despite all of the events in his life on and off the field.
"If that wasn't the case, Celtic would have replaced him long ago.
"It's clear that Gordon Strachan wishes to keep him. But I really believe that, for the sake of Artur's career, he should play in a bigger, more demanding league.
"If Newcastle make an offer for him, and Celtic accept it, then I think he should take the chance with both hands. He is at a stage where he needs a new challenge."