As well as the two previously mentioned players, Luke Shaw, Anthony Martial, Victor Lindelof, Paul Pogba, Axel Tuanzebe and Scott McTominay were not spotted at the hotel on Tuesday morning either; though it is expected that they will all play a part in the match against Burnley.
"Of course, it depends on many factors, but we open the door for what I call the December injuries".
During his five year spell with the club, he became an influential member of the Belgian First Division side, captaining his side on a regular basis, but serious injuries scuppered his chances of a big move.
When it was pointed out United have spent heavily - roughly £286million - since Mourinho took charge in 2016, the Portuguese said: "OK, (but) it is not enough".More news: Apple Is Purposely Slowing Down Older Phones , Says Geekbench
"The big historical clubs, they are normally punished in the market due to their history".
Last Saturday's 2-2 draw at Leicester was the first of four top-flight games in 10 days for United.
Smalling played the full 90 minutes in his side's 2-2 draw against Leicester City on the weekend.
"We should have won, yes". "That is what we are having now, lots of "s" goals against so that has an impact in the game". I take satisfaction by the way the team played, by the way the team reacted, to try to recover from 2-0 down.
He said: "At 2-0, it makes things more hard at half-time, I need my players to believe in them [selves] and I need them to believe in me; to accept the risk and not be afraid to lose three or four".