Asked whether Nkunku is back, manager Mauricio Pochettino said: "No. I hope he is back soon but he is not involved tomorrow, no.
"It's like I always tell you, sometimes we have been excited seeing him on the pitch and have him as soon as possible but we need to be careful. When he is ready, he will be ready."
He added: "Romeo Lavia like Christopher is not going to be involved tomorrow.
"Lesley [Ugochukwu] felt something last week and Noni was injured post-match after Brighton. They are minor problems and we hope they will soon be available."
Erik Ten Hag is under pressure at United, having overseen the club's worst start to a season in 50 years. The build-up to Wednesday's game has been dominated by reports of unrest in the Old Trafford dressing room.
"He is a fantastic coach," Pochettino said, giving his backing to Ten Hag. "I remember facing him with Tottenham in the semi-final of the Champions League against Ajax.
"Everyone was talking about Ajax; he is a fantastic coach and manager. It is good to see him after four years as we haven't seen him. We need to be respectful not to talk about what is going on at different clubs. I am happy here and we are dealing with many things we must improve on also.
"It's always good to play at Old Trafford; an amazing stadium, team, fans and club. We are all at a similar level with our different situations. I don't say it is a good moment to go there.
"We must be ready to compete and face a good team that is going to be tough because they, for sure, want to win. We want to build momentum from Brighton and be higher in the table. If we want to be in a different position, we have to go there to win.