Islam Slimani has suffered a "setback" and is facing an extended spell on the sidelines.
Rafa Benitez had hoped that the Newcastle United striker, signed on loan from Leicester City last month, would be available for tomorrow's game against Bournemouth.
However, Slimani – who arrived at the club with a thigh injury – will be sidelined for "at least" another fortnight.
United manager Benitez said: "We have good news. Almost everybody is available apart from (Jesus) Gamez.
"Slimani had a setback the other day, so he will not be available.
“It will at least be a couple of weeks. We have to be careful with him, because he had a problem when he arrived."
Slimani arrived on transfer deadline day last month.
“We worked really hard to try to bring players in to give us something different in the Premier League," said Benitez.
"We knew he was carrying a small injury. He’d had little problems, but in the last day he had to stop and check again.
"Everyone was expecting him to make the difference, but after the game against Manchester United we at least feel we have enough quality in the squad.
"Hopefully he will still help us in the next game."
Asked about signing a player with an injury, Benitez said: "When you go to the last day (of the window), it's always a risk.
"We did it and now we have to manage in the best way possible. He trained really hard. I was talking with him and he was positive. When he was feeling well, he was training really well, but then he felt this little problem."