The 24-year-old is currently half way through his season-long loan deal at Villa from Manchester United, but there is a clause in his contract that allows the £5 million rated goalkeeper to cut short this loan deal for a permanent move in January.
The Preston-born shot stopped has been mightily impressive between the sticks for Aston Villa this season and is one of the reasons why the Birmingham-based club currently find themselves in the play-off positions.
Due to all this interest, United are currently in the process of trying to extend his contract, which expires in six months, so that they can get as much as much money for him as possible.
Steve Bruce is extremely keen in signing Johnstone permanently, but the allure of the Premier League could be too much to turn down. Should he depart in January, Villa might struggle to get a like-for-like replacement as they are close to breaking Financial Fair Play regulations.