Rafa Benitez's sweating on the fitness of Vurnon Anita ahead of Newcastle United's visit to Villa Park.
Anita left the field with an injury late in Saturday's 1-0 win over Crystal Palace.
The midfielder – who has been filling in for the injured Daryl Janmaat at right-back – was replaced by Jonjo Shelvey in the 88th minute.
With Janmaat, sidelined with the hand and groin injuries he suffered at Southampton last month, unlikely to be fit for Saturday's must-win game against Aston Villa, United manager Benitez needs Anita to be available.
Janmaat – who fractured his hand punching a door at the St Mary's Stadium and is yet to rejoin full training – will need to wear a protective cast if he is to play again this season.
Asked about Janmaat last week, Benitez said: "Janmaat is close. He needs protection. He needs to be better and a bit more confidence."
Anita has impressed at right-back in recent weeks for relegation-threatened Newcastle, who moved out of the bottom three on Saturday.
"He’s a player that you can trust,” said Benitez. “He always will give you everything and also the understanding of the game and the things that we are trying to do.
“He’s very focused and he’s helping a lot when we have some problems like we have now in defence.”
Jamie Sterry, Newcastle's only other right-back, suffered a hip injury last month.