Everton are expected to be without Seamus Coleman until October following the ankle injury he suffered in pre-season.
The Republic of Ireland international was forced off by a bad challenge from Carlos Marchena during Friday's friendly against Villarreal and further scans have revealed the ligament damage.
Coleman is now facing two months on the sidelines and his absence will be a major blow to David Moyes, who is already working with one of the smallest squads in the Premier League.
Speaking on Twitter, the 22-year-old said: "Disappointed to miss the start of season, but injuries are part of football! Going to do everything possible to get back fit as soon as I can. Got to stay positive!"
Coleman would have missed the first two games of the new Premier League season anyway, after picking up a suspension following his sending-off against Chelsea on the final day of last term.