Brighton boss Roberto de Zerbi admits Ansu Fati faces three months out.
The on-loan Barcelona attacker was forced off in the win against Nottingham Forest a fortnight ago.
De Zerbi didn't specify the injury, but confirmed: "The news about Ansu Fati is I think he needs three months from the day of the injury.
"It's bad news for us because he was playing better, he was understanding better the idea. I'm sorry for him, I'm sorry for the team."
Fati has scored four goals in 14 appearances in all competitions for Brighton.