Everton forward Dominic Calvert-Lewin has been ruled out for up to two months with an ankle injury.
The 19-year-old had to be substituted after just 12 minutes during the Toffees' 3-0 win over Southampton on Monday.
Speaking at a news conference ahead of his side's FA Cup tie against Leicester City at the weekend, Ronald Koeman said: "Calvert-Lewin is out for up to seven to eight weeks."
The manager also confirmed that James McCarthy had not yet resumed training following a hamstring injury, while goalkeeper Martin Stekelenburg will also miss out.
Calvert-Lewin joined the Toffees on August 31 last year from League One outfit Sheffield United.