Nadia Petrova pulverised world number three Agnieszka Radwanska's defence of the title by beating her in the final to win the Pan Pacific Open tennis tournament on Saturday.
The Russian, who stormed back from one set and 1-4 down to beat sixth seed Sara Errani and went on to beat eighth seed Samantha Stosur in the last two rounds, pulled off yet another upset by scoring a 6-0, 1-6, 6-3 victory over the Pole.
"I feel amazing. This is the biggest tournament I ever won, and this is a great accomplishment," said a jubilant Petrova.
"At the beginning of the tournament, I didn't expect to be here, because I had a back injury, so it's delightful to be here right now.
"I used so much energy in the first set and it took a while to get back into the game, and the change of the court helped me a little bit to think about what I needed to do in the third set," she added.
Petrova fired a sizzling service return winner on a break point to take an early 1-0 lead before whitewashing the first set by finishing off with an ace on her second set point.
Radwanska had to save four break points to finally keep her service in the first game of the second set and pulled off her first break when Petrova hit a forehand into the net to move up 2-0.
Petrova lapsed into making errors and took only one point each in the following three games before keeping the sixth game, but Radwanska hit three aces in a row and a service winner to comfortably even it at one set all.
Neither had a break chance in the final set until the score went to 4-3 for Petrova, who took a break point in the eighth game thanks to Radwanska's two double faults.
Petrova broke the game with a backhand winner to go up 5-3 and calmly served out for the match, hitting a forehand volley winner on her second match point.
The veteran 30-year-old Petrova, whose only previous win over Radwanska also came from Tokyo in 2008, improved her record against the Pole to two wins against three defeats.
It was also Petrova's second title of the season, following her victory at 's-Hertogenbosch, and 12th overall.
The victory brought Petrova the winner's cheque of $385,000 and now she will move up to 14th in the world from 18th this week.
The 23-year-old Radwanska, who became Poland's first Grand Slam finalist of the Open Era at Wimbledon this season, had to be satisfied with the runner-up prize of $192,000.