'It's unbelievably frustrating,' he said. 'The morning of my first round, and I can't play and can barely walk. You've got to laugh or cry, and I don't feel like crying this morning.'
Quigley said the best-case scenario was a couple of days of recovery. He plans to play next week in the FBR Open.
He was replaced at the Buick Invitational by Kenneth Ferrie of England. Charlie Wi also withdrew Thursday with an illness and was replaced by Brad Elder.
Quigley walked his first 18-hole round Monday at Torrey Pines, but said the pain in his tailbone increased the last two days. He described it as a cyst and was trying to see a doctor in San Diego or go to the emergency room.
Quigley had surgery in September to repair torn knee ligaments. Missing the final two months of the PGA TOUR season caused him to fall from the top 125 on the money list. He was granted a medical exemption, giving him seven tournaments to earn about $63,000 to regain full status and qualify for THE PLAYERS Championship.