Colombia?s Radamel Falcao appears set to miss the World Cup after Monaco confirmed the striker will require surgery on a cruciate ligament injury.
Falcao, 27, was carried off during Wednesday?s 3-0 French Cup win at Chasselay Monts d?or Azergues after he was tackled by defender Soner Ertek.
A Monaco statement read: ?Following medical examinations, it appears that he has an injury of the anterior cruciate ligament in his left knee.
?Surgery is needed in the coming days.?
Recovery time for a serious ACL injury is usually between six and nine months.
Falcao has scored nine goals in 17 appearances this season since making a ?50m move from Atletico Madrid last summer.
He also managed nine goals for Colombia during World Cup qualifying to help the South American side book their place at Brazil 2014.
His injury represents a major blow for the national side, whose first match is against Greece on 14 June, and could also damage Everton?s chances of landing Monaco forward Lacina Traore on loan.
The Toffees had been granted a work permit for the 23-year-old Ivory Coast striker who had passed a medical despite a minor hamstring injury.
?We are still working on the Traore deal but there?s nothing to announce yet,? said Everton manager Roberto Martinez. ?We hope the Falcao injury won?t affect the decision to let Lacina go out on loan.?
The injury could also hinder Monaco?s hopes of winning a first French league title since 2000, as they already trail Paris St-Germain by five points.
Monaco coach Claudio Ranieri criticised the referee on Wednesday for allowing the match to continue while Falcao was injured.
?When you play against a team from a lower division, they are going to play really hard,? Ranieri said. ?That?s normal, and that is what I tell my players before the match.
?But if Falcao has something serious, it is the referee?s fault.
?Everyone wants to play like in England and let the game go. It?s not possible here. The referee must see when there is a foul and blow his whistle.?