Northampton hooker Dylan Hartley has been ruled out of England's tour of Australia and New Zealand due to a knee injury.
The 24-year-old suffered the injury to his left knee during Saints' 21-19 defeat to Saracens in Sunday's Guinness Premiership semi-final at Franklin's Gardens.
A scan revealed Hartley will require an arthroscopy to treat the damage to his cartilage. His place will be taken by Leicester's George Chuter.
The news will come as a major blow to Hartley, who has grown in maturity since being handed the Northampton captaincy at the start of the season.
Under the New Zealand-born forward's guidance the club won the LV= Cup and reached the quarter-finals of the Heineken Cup, while his form has seen him start England's last seven Tests, taking his caps total to 19.
Brive front-rower Steve Thompson and his Bath counterpart Lee Mears are the most likely men to take Hartley's place in the two upcoming Tests against Australia, with Chuter and Wasps' Rob Webber also among the touring party.
An RFU statement read: "Dylan Hartley saw a specialist yesterday and had a scan on a left knee injury.
"The results of the scan concluded that Dylan requires an arthroscopy in order to treat some damage to his cartilage.
"The injury was sustained in Dylan's last game for Northampton Saints against Saracens in the Guinness Premiership semi-final.
"Dylan is therefore out of the tour to Australia and New Zealand and his place in the Senior England EPS will be taken by George Chuter."
The RFU have also confirmed the withdrawal of three players from the England Saxons squad for the Churchill Cup.
Wasps flanker Tom Rees, who saw his season ruined by a shoulder injury, will stay at home to continue his rehabilitation with Leeds' Kearnan Myall his replacement.
Bath lock Stuart Hooper is replaced by Newcastle's James Hudson after suffering a toe injury in his club's semi-final defeat at Leicester on Sunday, while London Irish hooker David Paice has failed to recover from a quadricep injury in time to tour. A replacement for the Exiles man will be announced at a later date.