Casey's season could now be over
Paul Casey retired after just two holes of the final round of the HSBC Champions tournament in China after suffering a recurrence of a rib injury.
The 32-year-old, who only returned to action last week after three months out, will now re-visit a specialist in America in a bid to solve the problem.
This latest setback means Casey's hopes of winning the inaugural Race to Dubai title are now in tatters.
He had been fifth in the Race to Dubai and in touch with leader Lee Westwood.
In a bid to remain in the hunt for a maiden order of merit title, Casey returned to action at the World Match Play Championship at the end of last month.
He lost all three matches in Spain but had been six under par through three rounds in Shanghai despite insisting all week he had still not fully recovered from the muscle injury.
He [Casey] very much felt he had a chance to win the Race to Dubai
Casey will now head to America to consult with his long-time specialist, with a decision on whether he will play in the season-ending Dubai World Championship later this month expected next week.
"He has felt pain before, but he felt it severely enough," said Casey's manager, Guy Kinnings.
"We always agreed that if he felt that he would stop. He is going to withdraw from next week and get back and see the specialist who he has been working with and get it scanned and have a look and see.
"He is sufficiently concerned to do that straightaway. He doesn't know if this means a recurrence and out for a while or just a worrying tweak."
Casey has already pulled out of next week's Hong Kong Open.
"He is hugely disappointed about not being able to play Hong Kong," added Kinnings.
"He very much felt he had a chance to win the Race to Dubai, that's why he had been aiming to come back last week and this week and play in Hong Kong."