Moscow:Maria Sharapova lost to teenager Victoria Azarenka 7-6 (9), 6-2 on Wednesday in the second round of the Kremlin Cup.
Sharapova was playing in Moscow for only the third time and has never made it past the second round.
The loss was Sharapova's first match in six weeks since her defeat in the third round of the U.S. Open. The second-seeded Russian had been sidelined because of a lingering shoulder injury.
Sharapova went ahead 5-3 and 40-love in the first set but lost 10 consecutive points and allowed Azarenka to force a tiebreaker.
"Maybe I was too self-assured at 5-3," Sharapova said. "But it all went downhill after."
The 18-year-old Belarussian saved three more set points on the tiebreaker before taking the set. Azarenka then broke the two-time Grand Slam champion twice in the second set for her first win over the fourth-ranked player.
"I tried to stay concentrated and believed I could win the match," said Azarenka, ranked 32nd, who was a runner-up in her first WTA Tour final in Tashkent last weekend.
Vera Zvonareva of Russia beat sixth-seeded Amelie Mauresmo 4-6, 6-3, 6-4 in the first round.
"She took the chances she got," Mauresmo said. "She began pretty bad and I was doing well, but then it went the other way."
In the second round, top-seeded Svetlana Kuznetsova was the only seeded women to win Wednesday after she rallied to beat Gisela Dulko of Argentina 3-6, 6-2, 6-4.
Vera Dushevina upset Wimbledon finalist Marion Bartoli 2-6, 6-0, 6-4, and Russia's Elena Dementieva defeated seventh-seeded Patty Schnyder of Switzerland 6-3, 6-4. Dementieva will face Azarenka in the quarterfinals.
In the men's event, second-seeded Mikhail Youzhny of Russia and third-seeded Andy Murray of Britain both advanced to the second round. Youzhny beat Ernests Gulbis of Latvia 6-3, 6-2, and Murray defeated Evgeny Korolev of Russia 6-2, 6-4. Fourth-seeded Paul-Henri Mathieu went through to the quarterfinals by defeating Russian qualifier Igor Kunitsyn 6-3, 6-4.
Both Kuznetsova and Dulko struggled to hold serve. Kuznetsova, the 2004 U.S. Open champion, converted only six of 16 game points for the win.
"It seems to me that I was playing against myself, surface and balls today, not against her," said Kuznetsova, who had four aces and 55 unforced errors. "I played bad but nevertheless won the match."
Mauresmo, who lost to Zvonareva for the first time in eight matches, took a 4-0 lead before winning the first set.
But the Russian broke the former top-ranked Frenchwoman in the second game of the second set and again in the opening game of the third. Mauresmo broke back at 4-4 but made three unforced errors on her serve in the next game, letting the 24th-ranked Russian serve for the match.
Bartoli took the first set before Dushevina won nine consecutive games to even the match.
In the third set, the Russian led 3-0, but Bartoli evened it 4-4 and, serving in the 10th game, saved a break point before losing.
Fourth-seeded Serena Williams is back at Moscow after a decade to look for her 29th career title. At the age of 16, Williams qualified and lost in the first round in 1997 when she was ranked 448th.
After a bye in the first round, Williams plays Tatiana Perebiynis of Ukraine in the second round Thursday.