But the ‘keeper, who is rated at around £5million, has the option in the agreement to cut short the loan spell if it would mean securing a permanent move in January.
According to the Mirror, West Ham, West Brom and Crystal Palace are all vying for Johnstone’s signature.
Sam Johnstone's reflexes ⚡⚡⚡ The training for shot stopping at Man United must be immense #avfc— Rajkiran S Mattu (@RajSMattu) December 17, 2017
West Brom are looking at Johnstone to add more competition for current No.1 Ben Foster, whilst West Ham are looking for a man to fill the void Joe Hart will leave once he returns to Manchester City at the end of the season.
Crystal Palace, the team most in need of a goalkeeper, will see Johnstone as a long-term investment, with Wayne Hennessey’s deal up next summer and 38-year-old Julian Speroni expected to make a retirement announcement within the next year or so.
Meanwhile, Villa boss Steve Bruce hasn't given up hope of turning Johnstone's temporary stay into a permanent one.
Johnstone was hailed as the man who rescued a point for Villa in the goalless draw with Millwall a fortnight ago, making eight saves in the match.