England and Wasps flanker Tom Rees will miss at least the majority of the Six Nations because of a knee injury.
Scans have confirmed the 24-year-old suffered a moderate tear of the medial knee ligament during Sunday's 24-18 Premiership win over Harlequins.
Rees will begin a period of extensive rehabilitation at Wasps.
Rees is not expected to return for a minimum of two months, ruling him out of England's matches against Italy, Wales and Ireland.
England face France on 15 March, while their last Six Nations game of 2009 is against Scotland on 21 March.
Meanwhile, Steffon Armitage and Lewis Moody have both been named as potential additions to Martin Johnson's EPS squad.
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