It's one thing to not start after a long spell out, that I think most of us will understand. But with games coming thick and fast, an ample opportunity to rest our first choice wide players (Anthony/Rashford), and a game at home against championship opposition, there's no better time to give him some minutes off the bench.
That he is not even in contention for the bench tells me he's not as close to a return as some people have been speculating. I could of course be wrong and he's on the bench on Wednesday, but it definitely is strange given we know nothing of the reason he's been away in the first place.