Sam Johnstone is United's third choice goalkeeper, behind David de Gea and Sergio Romero, but has not played a competitive game for them yet. United manager Jose Mourinho wants him to go out on loan to gain more competitive experience.
Mourinho has recalled young goalkeeper Joel Pereira from his loan spell at Portuguese club Belenenses to provide cover for de Gea and Romero. 20-year-old Pereira made 8 appearances this season for the Portuguese side and also plays for Portugal U20.
Aston Villa manager Steve Bruce has been reported to have been targetting Johnstone since he first took over at the club in October 2016.
Johnstone, who came through United's academy, has had loan spells at a number of clubs, including Oldham, Scunthorpe, Doncaster, and most recently, Preston.