Ronnie O'Sullivan could be forced to pull of the UK Championship at York's Barbican Centre after twisting his ankle.
The absence of the five-times world champion and snooker's biggest draw - who won the sport's second biggest event in 1993, 1997, 2001 and 2007 - would be a huge blow to tournament sponsors Coral and snooker fans.
O'Sullivan is a strong favourite to win the event, but admitted he might have to play on one leg in his first-round match against Daniel Wells of Wales on Thursday.
O'Sullivan is an avid runner, and has suffered several injuries over the past year because of his daily training schedule.
In his latest Eurosport blog, O'Sullivan admits he is relishing the chance to win a fifth UK title that would see him draw level alongside Stephen Hendry and leave him one adrift of Steve Davis' haul of six UKs.