If Man United plans to sell the German in the January transfer window then it would make sense to let him play a few games.
It is totally not worth it, he is no longer the same person as few years ago and he is only worth few millions pounds now . The reason that he was left out of the squad was because he had injury before otherwise he could still be a regular player on the team, as van gaal always had him as one f his first option
Mou is different from Van Gaal, it is not a guarantee that Bastian will play regularly in Mou's era even though he is fit.
Mou is so bad in selecting starting XI this season, he cant find the best strategy for MU till this time. He is not the special one anymore. That's all..
That may or may not be true depending on how you see their current predicament. But let me ask you, what starting XI would be good for Man United right now that would perform well or at least be decent week in and week out?