Oosthuizen said he started to feel “tension” in the knee during the final round last Sunday at the BMW Championship, but had treatment Monday in South Florida and didn’t expect it to be a problem at East Lake.
About seven holes into his opening round, however, he started to feel tightness again and said he decided to stop playing when the ailment began affecting his swing.
“It came back really quickly,” he said.
Oosthuizen, who is the second player to withdraw from the finale after Jim Furyk pulled out earlier this week with a wrist injury, is currently 29th on the FedEx Cup point list and will receive last-place money and points at the Tour Championship and whatever bonus he’s earned from his finish on the season-long point list.
On Wednesday evening the South African went to a local hospital to have a ganglion cyst in his right wrist drained, but said his wrist didn’t bother him Thursday.
“It might mean missing next week but it’s tough because I need my numbers [13-event minimum] in Europe,” Oosthuizen said. “But I should be fine for the Presidents Cup.”
If Oosthuizen is unable to play the Presidents Cup International captain Nick Price would be allowed to pick a replacement.