The 23-year-old Mattek, from Miami, was ranked 153rd in the WTA Tour rankings on April 7 after losing six of seven matches to open the season. But she made it to the semifinals of a grass-court tournament in England before losing to Serena Williams in the round of 16 at Wimbledon, moving her into 59th place entering this $600,000, 56-player event.
Mattek's win over Vaidisova was her ninth in 11 matches, including a 6-3, 6-0 win over Vaidisova in England. Mattek's third-round opponent Thursday will be Olga Govortsova of Belarus, who upset No. 6 Daniela Hantuchova of Slovakia on Tuesday.
Fourth-seeded Dinara Safina of Russia also moved into the third round, beating Shuai Peng of China 6-2, 6-2. Eighth-seeded Victoria Azarenka of Belarus, No. 9 Nadia Petrova of Russia, No. 10 Nadia Pennetta of Italy and No. 14 Sybille Bammer of Austria also advanced.
Howver, seventh-seeded Patty Schnyder of Switzerland was another upset victim, losing to veteran Ai Sugiyama of Japan 6-4, 7-5; and 122nd-ranked Meng Yuan of China eliminated No. 16 Sania Mirza of India, 6-4, 6-3.
Mattek said her turnaround has been primarily due to being physically fit and able to play more often and more consistently.
"I attribute a lot of it to my fitness level,'' she said. "I think I'm in the best shape of my career right now. I've played a lot of matches and that's made me mentally tough.
"I've been able to fight my way through matches. I've stayed a lot healthier this year. Last year I'd win a match 7-6 in the third (set) and then be dead for the next match. Plus when you're playing the top girls week in and week out you get a feel for their game. It's a lot faster, but you get used to that pace. I've had a great couple of months.''
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