Memphis, TN -- Czech Republic qualifier Petra Kvitova upset top-seeded and defending champion Venus Williams 2-6, 6-4, 6-3 in one hour and 36 minutes Tuesday night in the first round of the Cellular South Cup.

The 17-year-old left-hander, who came in ranked No. 143, won her second career (2-2) Sony Ericsson WTA Tour match. She kept Williams off-balance the last two sets with an effective serve and ground game. After losing serve twice in the opening set, Kvitova only lost serve once the rest of the way.

"She mixed it up really well and I didn't return well," said Williams. "She has a good serve and she played well. I am disappointed I won't be here the rest of the week."

Kvitova converted four of 10 break points, including three of four in the final set. Williams went up 2-0 in the final set but Kvitova won the next four games and closed out the match with a backhand return service winner on match point.

"I am really happy and I was very nervous in the first set," said Kvitova. "I started to believe I could win this match in the third set. I didn't think I could do it in the first set. I served very good and it's the best match I've ever played."

Earlier in the day, American Bethanie Mattek upset No. 2 seed Tatiana Golovin of France 6-4, 6-4, in the first round to post her first match win of the season (1-3).

"This year I've actually been playing pretty good," said No. 148th-ranked Mattek. "I was sick in Australia and I played an awesome match in Chile (losing to Jelena Kostanic). I had match points there. It just didn't go my way.

On jumping out to a 5-1 lead in the first set, Mattek added, "I honestly was seeing the ball really well. I was there on every shot she hit. She started mixing up balls more in the second set (but) I stuck to my game plan the whole match."

Mattek converted five of 10 break points while saving three of five break points on her serve in the one hour and 26 minute match.

No. 3 seed Shahar Peer of Israel moved into the second round with a 6-2, 6-1 victory in 62 minutes over American Ahsha Rolle.

Peer, last year's Memphis runner-up, converted five of eight break points while losing serve only once. Peer broke away from a 3-2 lead in the opening set to break in the sixth and eighth games. In the second set, she broke Rolle three times.

She will take on Melinda Czink in the second round. The 20-year-old improved to 10-5 on the season.

No. 6 seed Caroline Wozniacki of Denmark needed only 56 minutes as she rolled to a 6-0, 6-2 win over Milagros Sequera of Venezuela. The 43rd-ranked Wozniacki converted six of nine break points and only lost serve once. Wozniacki won 77% of first serve ponts compared to Sequera's 48%.

In one of two second round matches, No. 5 seed Olga Govortsova advanced to her first WTA Tour quarterfinal of the season as she rallied to defeat Renata Voracova of the Czech Republic 4-6, 6-4, 7-6(5) in three hours and five minutes. The 19-year-old from Belarus saved one match point serving at 30-40, 4-5 in the third set. Both players held in the next game, forcing a tie-break. Govortsova took a 3-2 lead in the tie-break and never looked back, winning 7-5.

No. 7 seed and 2006 champion Sofia Arvidsson also came back from a set deficit to reach the quarterfinals with a 1-6, 7-5, 6-3 win over Canadian Stephanie Dubois. The 71st-ranked Swede improved her match record to 12-5 on the season and 9-2 in Memphis.

Monday: Davenport Avenges Loss to German Teenager