Casey has not yet set a comeback date, said his manager
Paul Casey will miss the Dubai World Championship, the event that could have resulted in him being crowned the European Tour's number one this season.
The world number five has taken advice not to risk further injury to the shoulder muscle he tore in July and will miss the event on 19-22 November.
Manager Guy Kinnings said: "It's sad. Paul's intercostal muscle is not torn again but it is inflamed."
Casey spent nearly three months out before returning a fortnight ago.
He lost both matches in the Volvo World Match Play Championship in Spain then withdrew early in the final round of last week's HSBC Champions tournament in Shanghai.
The 32-year-old, who lies fifth on the Race to Dubai money list, flew from China to the United States for an MRI scan in the hope that he would be given the all-clear to compete in the Middle East.
He will now seek a further opinion before making a decision on when he will be fit enough to return.
The Dubai event is for the leading 60 money-winners on the circuit but the field will now be only 58 as American Anthony Kim, runner-up to England's Ross Fisher at the Match Play in Spain, has decided not to play.