Wimbledon champion Venus Williams suffered a shock 4-6, 7-6, 6-4 defeat by France's Virginie Razzano in the Japan Open final on Sunday.
The top seed, who won last week's Korea Open, squandered three match points in the second set tiebreak before Razzano levelled the Tokyo final at one set apiece.
Former world number one Williams, bidding for a 37th career title, called an injury timeout for treatment to her right thigh after the first game of the decider but it made no difference.
Razzano's tenacity earned her the decisive break at 5-4 in the third, and the fifth seed sealed a stunning upset by forcing Williams into another wild forehand after two hours, 48 minutes.
It was Razzano's second title on the WTA Tour and comes just a week after her breakthrough win in Guangzhou last week.