The Red Devils manager fielded a makeshift back three for the draw against Southampton on Saturday with midfielders Scott McTominay and Nemanja Matic lining up alongside Phil Jones.
Centre-backs Chris Smalling, Victor Lindelof and Eric Bailly were ruled out, and Marcos Rojo was only deemed worthy of a place on the substitutes' bench.
Left-back Luke Shaw was forced off with an injury, while Ashley Young picked up a yellow card that means he is suspended for the Gunners' visit to Old Trafford.
Mourinho suggested Jones, only recently returned from injury, is struggling again and said that, as he did at Southampton, he will leave his team selection as late as possible to give his walking wounded as much recovery time as he can.
"Against Southampton, three hours before the game I don't know the team that is going to play," he said.
"We were waiting and waiting to see who could [play] and who could not. And we are in a very similar situation this time.
"If the game was at 11 o'clock [in the morning on Tuesday], I would say Chris Smalling is not playing, Eric Bailly is not playing, Phil Jones is not playing, Victor Lindelof is out of the question.
"Antonio Valencia is not playing, Luke Shaw is a doubt, Matteo Darmian is back, but I have to wait, I have to select probably everybody again and take everybody again.
"Maybe [on Wednesday] we have to decide, like in the last match, with a couple of hours before the game."