Yani Tseng overslept on Wednesday and missed her 9:10 a.m. pro-am tee time. As a result, Tseng was withdrawn from the Kia Classic, per LPGA regulations.
Tseng, who lost her world No.1 ranking last week to Stacy Lewis, was the defending champion in the tournament at Carlsbad, Calif. She is traveling this week without manager Naya Hsu, who is typically by Tseng's side. Hsu is back in Taiwan on business.
"I'm embarrassed to admit that I wasn't feeling well last night and accidentally overslept and missed my tee time for the pro-am this morning," Tseng said in a statement. "I was extremely excited to compete this week to defend my title at the Kia Classic and to try to regain the No. 1 spot.
"This was an unfortunate mistake and I want to apologize to Kia, my sponsors and all of the fans."
Tseng will compete next in two weeks at the year's first major, the Kraft Nabisco Championship.
Golfweek's Beth Ann Baldry contributed to this report.