(CNN) -- Russia's Nadia Petrova stunned Agnieszka Radwanska of Poland in the Pan Pacific Open final in Tokyo on Saturday winning in three sets 6-0 1-6 6-3.
The 30-year-old stormed into a one-set lead, breaking the world No.3 three times in the opening set before Radwanska rallied in the second.
The final set was more evenly contested with Petrova claiming a decisive break in the eighth game to lead 5-3, before holding serve to seal her second title of the season.
"I feel amazing. This is the biggest tournament I ever won and this is a great accomplishment. 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," Petrova said.
Defending champion Radwanska, who reached her first Grand Slam final at Wimbledon earlier this year, accepted that the better player had prevailed on the day.
"Her biggest weapon is her serve, for sure, but to be honest, her return was not bad today. I really had to serve very good to win my game, so her serve and return were really working for her today," the 23-year-old said.
"I was really trying to get the title again this year, but unfortunately she was playing too good," she added.
The victory sees Petrova move up four places in the world rankings to No.14.