TOUR officials did not have details on Immelmans illness, saying only he had already returned to Orlando.
Since winning the Masters by three shots over Tiger Woods, Immelman has had a tough time. He has failed to break par in his last two tournaments, missing the cut at the EDS Byron Nelson Championship and the Wachovia Championship.
Woods, the PGA champion, withdrew earlier because he is recovering from knee surgery.
Immelman was replaced by Dustin Johnson, a 23-year-old rookie.