Former England prop Andrew Sheridan could be forced to retire due to a neck injury, according to Toulon coach Bernard Laporte.
The 34-year-old loosehead suffered the injury during the second half of Toulon's 15-9 victory over Perpignan in the Top 14 last month.
Laporte confirmed that Sheridan, who won 40 England caps and was selected for two British and Irish Lions tours, will be sidelined for one month and then reassessed.
"Andrew is out for a month and possibly forever," said the former France coach.
"He has always had a problem between his neck and his shoulder. The surgeon has told him that it's not necessary to have a new operation.
"He will now have a month of complete rest and if the pain doesn't go away, then he will have to stop playing rugby."
Bromley-born Sheridan began his career with Richmond before moving to Bristol in 1999, where he made more than 50 appearances and was converted from a lock into a prop.
Sheridan moved north to Sale Sharks in 2003, where he made scored eight tries in 113 appearances and won the European Challenge Cup in 2004 and Premiership title in 2006.
He underwent four shoulder operations inside two years during his time with the Aviva Premiership club, and declined an insurance payout in 2011 to continue playing.
Sheridan moved to Toulon in 2012 and started in last season's Heineken Cup final victory over Clermont Auvergne.