Losing his place in his national side has been a major blow to Krul, who recognises the need to be playing in European competition to remain in the frame for an extremely competitive Holland squad.
He looks certain to miss out on the World Cup in June.
He has had a host of big-name European clubs watching him in recent weeks.
Newcastle are braced for a busy summer and expect to receive interest in some of their bigger names.
They are aware that Tottenham, who are expecting interest in Hugo Lloris, have identified Krul as their main target in the event that the France goalkeeper requests a move.
Celtic’s Fraser Forster – who would welcome a return to Newcastle – has also been considered by Newcastle if Krul departs.
He has made it known he wants to play in the English league, preferably with Newcastle.