Roberto Martinez has revealed that up to five Belgium players could be allowed to leave the squad to sign with new clubs this week.
The transfer window shuts on Thursday when the Red Devils are scheduled to play Gibraltar.
But Martinez is aware of the possibility that some players may miss the game if a deal has to be completed.
"We need to bring a bit of reality to the situation, the 31st August is the deadline day for a few markets." he added.
"That is something I took into consideration when we called a squad of 28 players because this is the reality that happens. Certain players, I would say five, in the squad could be in a position where they change their clubs.
"I remember the first time I signed Romelu Lukaku was on August 31st and he was sharing the room with Kevin Mirallas in a hotel in Scotland, and I know these things happen and it would be stupid to go against it.
"We need to help the players find the right outcome."
Belgian reporter Kristof Terruer, via the Sun, claims that Liverpool duo Simon Mignolet and Divock Origi, Everton forward Kevin Mirallas, Barcelona defender Thomas Vermaelen and Anderlecht midfielder Leander Dendocker are among the players that could make a move on before deadline day.