The 23-year-old is third choice behind David de Gea and Sergio Romero at Old Trafford but is highly thought off and was handed a new contract running until the summer of 2018 last month.
United boss Jose Mourinho now wants Johnstone to get some more first-team experience under his belt and is planning to send him out on loan in the new year.
Villa and Wigan are both set to be at the front of the queue, with the Latics desperately searching for a new shot stopper after recently losing Adam Bogdan to a season-ending injury.
Villa boss Steve Bruce is keen on Johnstone as he looks to bolster his goalkeeping options in January.
Wigan will hope they have the edge on the Villans if it comes to a straight fight, having recently appointed former United coach Warren Joyce as their new manager, Johnstone having worked with Joyce while part of the Red Devils' reserve team.