A day before turning 40, Japan's Kimiko Date Krumm bundled defending champion Maria Sharapova out of the Pan Pacific Open in the first round on Monday.
Date Krumm produced a shock 7-5, 3-6, 6-3 victory over Russia's former world number one, who squandered three points for a 4-2 lead in the final set.
"Playing against a player who used to be number one and the defending champion I knew I had to play my best," the 1995 winner Date Krumm said.
"I just got back from Korea yesterday and felt really tired but my body felt a little better today," added the Japanese, who reached the quarter-finals in Seoul last week.
Sharapova broke to take a 3-2 lead in the final set but buckled when up 40-love in the next game, double-faulting twice en route to surrendering her own serve.
"Momentum is so big in tennis," said the three-time Grand Slam winner, who is still struggling to return to the top of the women's game after shoulder surgery in 2008.
"If you give your opponent a chance they can get confident and take the momentum away."
Sharapova, who committed 11 double-faults in total, praised the fitness of her opponent, who returned to professional tennis in 2008 after 12 years away from the game.
"It's incredible," said Sharapova. "It just shows you how she has stayed in such great shape while away from the game. She is incredibly fit."
Seven of the world's top 10 women's players are competing in Tokyo this week at the $2 million tournament.
