Watford coach Walter Mazzarri has doubts over Roberto Pereyra's fitness after the midfielder suffered an injury in Wednesday's defeat to Manchester City.
Pereyra appeared to suffer a knee injury early in the game but tried to play on before eventually leaving the pitch in the 30th minute.
Mazzarri suggested it could be the latest in a series of serious injuries for the Hornets.
"I asked him if he felt a twist in the knee, they [medical staff] told me it was a knock and that's the reason he went back on the pitch. Now, I'm not sure," Mazzarri said.