Lucas Paqueta, a midfielder for West Ham, may be out for "at least two months" due to a calf injury.
The Brazilian was hurt against Arsenal at the end of December, and the problem returned in Sunday's FA Cup draw against Bristol City.
He only played 14 minutes in the Bristol City match and missed the goalless draw with Brighton on January 2.
Paqueta is scheduled to see a professional to assess the severity of the issue.
Manager David Moyes would suffer greatly if Paqueta were to miss out because he was a vital contributor to West Ham's 2023 comeback.
In June, West Ham won its first trophy in forty-three years after Jarrod Bowen's game-winning assist set up the team's victory against Fiorentina in the Europa Conference League final.
Bowen, meanwhile, will also miss a few games after needing assistance leaving the field on Sunday due to an ankle issue.
Even though the damage is not as bad as first thought, Bowen is not anticipated to be fit for the Premier League trip to Sheffield United the following weekend and will likely miss the replay against Bristol City at Ashton Gate on January 16.
Due to injuries, West Ham now lacks Mohammed Kudus, another offensive option, as he is with Ghana at the African Cup of Nations. Veteran Michail Antonio has also had a setback in his recovery from a knee injury he sustained while playing for his country in November.