Casey withdrew Sunday after a triple bogey on the par-5 second hole.
He is No. 5 in the Race to Dubai, and this all but assures he will not be able to compete for the $7.5 million bonus. His agent, Guy Kinnings, said Casey was headed back to his home in Arizona and would not play next week in Hong Kong.
Casey first injured his ribs at the British Open and did not play again until the World Match Play Championship last week.