Celtic are identifying alternative goalkeeper options as Fraser Forster continues to mull over a contract offer.
BBC Scotland understands the club are keen on the former Sunderland and Hearts number one Craig Gordon.
Former Celtic keeper Artur Boruc and Blackburn's Paul Robinson are also on the shortlist.
Forster remains a Newcastle United player but a fee has already been agreed between the clubs.
The 24-year-old Englishman has made 90 appearances in his two seasons at Celtic Park and helped the Glasgow outfit win the Scottish Premier League title this term.
He previously had loan spells at Stockport County, Bristol Rovers and Norwich City.