Sam Jones' hopes of making his England debut have been put on hold after it emerged his broke his right leg during a judo session.
The 24-year-old Wasps flanker had been pushing for a place in Eddie Jones' side for the autumn internationals after he was called into England's training camp in Brighton this week.
However, he is now set to miss the series after the training mishap.
It is understood Jones and Maro Itoje were putting into practice what they had been taught by British Judo coaches JP Bell and Kate Howey when injury struck on Tuesday morning.
Jones had been in contention to feature at openside flanker in England's November series, but must now instead wait to discover how long he will be sidelined.
The Rugby Football Union (RFU) initially said Jones had suffered ankle damage, but Wasps released a statement on Wednesday confirming the fracture to his right leg.
"Following an X-ray, Wasps can confirm that back row forward Sam Jones has suffered a fracture of his right leg, fibula, during England training," said Wasps' statement.
"The club is awaiting the results of subsequent MRI scans and Jones will see a specialist on Friday afternoon to determine the extent of the injury."
Wasps rugby director Dai Young admitted Jones had suffered wretched timing with the injury after forcing his first senior England call.
"It's a big blow and I really feel for Sam, because he has worked his socks off for Wasps and deservedly got his call-up to England," Young said.
"Sam has been one of the first names on my team-sheet this season.
"These things happen, but you can't help but feel sorry for him. It's too soon to know how long he will be out, but our medics and physios will look after him and we look forward to having him back when he is ready."
Jones' injury denies him the chance, in the short term at least, to compete with Leicester's Mike Williams for first refusal on England's vacant number seven shirt.
Wasps' James Haskell remains sidelined after toe surgery, leaving the openside role up for grabs. England boss Eddie Jones wants a "destructive defensive player" at seven in the absence of a "natural" openside.
Saracens' versatile lock Itoje could yet move out to the flank, with Chris Robshaw continuing at blindside and Billy Vunipola at number eight.