Everton have confirmed left-back Lucas Digne is set to go undergo surgery after suffering an ankle ligament injury in training.
"The left-back was injured during a training session at USM Finch Farm this week," an Everton statement read on Thursday.
"Digne is due to undergo surgery on Monday before commencing his rehabilitation under the care of the club's medical staff."
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The 27-year-old France international has been a stand-out performer in the Toffees' strong start to the season, with Carlo Ancelotti's team currently sixth in the Premier League table.
Digne has missed only five league matches since he joined the club in the summer of 2018 from Barcelona in an £18m deal.
One of them came this season, after his sending-off at Southampton saw Ancelotti employ new signing Niels Nkounkou at left-back.
The 20-year-old arrived on Merseyside from Marseille in the summer and made his first top-flight appearance of his career at St Mary's.
Everton also have midfielder Jean-Philippe Gbamin out with an Achilles injury and club captain Seamus Coleman sidelined through a hamstring issue.
Ancelotti's side face a tough run of fixtures in December as they host Chelsea, Arsenal and Manchester City in the Premier League, as well as a trip to Leicester City and the Carabao Cup quarter-final tie at home to Manchester United.