"Angie has had a long season. I didn't expect to win that easily but I was ready to turn it around and get a win against her." Kerber said she felt some discomfort in her shoulder but refused to use it as an excuse for her shock loss.
"I was not playing my best tennis, I know I can play better," Kerber, said. "It's a long season and we've been playing 10 months - a lot of matches.
"I felt the shoulder but it's not an excuse. I was not serving my best. I had a lot more double-faults than is normal for my game." Kerber now turns her focus to the year-end championships starting in Singapore in just over a week.
Seventh seed Caroline Wozniacki reached her third semi-final in a month, defeating China's Wang Qiang 6-3, 7-5.
Defending champion Jelena Jankovic fought a see-saw battle with Alize Cornet, finally winning 3-6, 6-4, 6-2 as Cornet ended with a 13th double-fault after more than two-and-a-quarter-hours.
- AAP