London Wasps flanker Tom Rees will miss the start of England's RBS 6 Nations campaign after it was confirmed he had suffered ligament damage in his left knee.
Rees, 24, is expected to be sidelined for a minimum of two months with a moderate tear to his medial ligament - ruling him out of England's games against Italy on February 7, Wales a week later and Ireland on February 28.
He will also miss Wasps' vital Heineken Cup pool fixtures against Leinster at Twickenham on January 17 and Castres the following Sunday.
Rees suffered the injury just three minutes after coming on as a replacement in Wasps' 24-18 Guinness Premiership victory over Harlequins at Adams Park on Sunday.
His absence could open the England door for the powerful London Irish flanker Steffon Armitage who is arguably the form openside in the country and has helped the Exiles to the top of the Premiership.
Armitage, 23, was included in the England Saxons squad in July after an impressive breakthrough season with the Exiles.
England manager Martin Johnson will name his new 32-man squad for the RBS 6 Nations on January 14.
Leicester flanker Lewis Moody is also ready to reclaim his place in the England squad having missed the summer tour and autumn internationals after suffering a ruptured Achilles and undergoing a hip operation.
Wasps' disappointment at losing Rees will be tempered somewhat by the performance of the destructive Serge Betsen in the openside position against Harlequins.
England Under-18 head coach John Fletcher insists his young side will be better for the experience after beating Italy in the bronze final to round out their 2015 Rugby Europe U18 Championship campaign in style.