SERENA Williams has lost her chance of a 23rd grand slam singles title and a record 187th straight week at number one in the world after a shock straight-sets semi-final defeat to Karolina Pliskova.
Willams lost 6-2 7-6 to the 10th seed from the Czech Republic with Angelique Kerber now moving to the top ranking following her defeat of Caroline Wozniacki 6-4 6-3.
The German would have moved to No.1 whatever the result against the Dane when the new rankings lists are revealed on Monday.
Williams, who lost in the semi-final to Italy's Roberta Vinci last year, was hoping to go past Steffi Graf in major tournament wins and also beat the German's record for 186 straight weeks on top of the pile.
Pliskova was the fourth women to defeat both Serena and Venus Williams in the same tournament as she moved through to the final.
The others were Martina Hingis (Australian Open), Kim Clijsters (US) and Justine Henin (US).
"I don't believe it,” said Pliskova, who had never made it past the third round of a Grand Slam in 17 prior attempts.
"I knew I had the chance to beat anyone if I played my game. I am excited to be in the final and to beat Serena as she is such a great champion.
"Even when she was down a set and break she was still fighting. I had to fight hard to win.”
The Czech's nerves almost got the better of her after leading 3-0 in the second-set tie-break.
She made three errors, including a double fault but despite leading 4-3 and 5-4 in the breaker, Williams could not convert and her sixth double fault handed the match to her opponent.
Pliskova pocketed the first set in 26 minutes without facing a break point.