American wild card Christina Mchale scored the biggest upset of the opening round at the 2010 Western & Southern Financial Group Women's Open on Tuesday when she defeated 2008 champion Nadia Petrova.
Mchale, who last week reached the semifinals at an ITF event in Vancouver, opened up a 7-6(4) 5-3 lead before the 15th seed Petrova retired citing heat illness.
Mchale will now carry the burden of being the lone American left in the draw when she faces Ayumi Morita of Japan on Wednesday in the third round.
Other seeds fared better on Tuesday, as No. 11 Flavia Pennetta and No. 12 Yanina Wickmayer both advanced with straight sets wins.
Pennetta, who reached the semifinals in Cincinnati in 2009, downed Australian Open semifinalist Jie Zheng 6-4 6-2. Wickmayer, a US Open semifinalist in 2009, defeated qualifier Greta Arn 6-2 6-2.
Russia’s Anastasia Pavlychenkova, who won the title in Istanbul in her last tournament, extended her personal winning streak to six matches with a 6-3 6-4 win over 2005 Cincinnati semifinalist Daniela Hantuchova.
In the lone second round match of the day session, No. 16 seed Marion Bartoli, the 2007 Wimbledon finalist, became the first player to reach the third round with a 7-6(4) 6-1 win over Alona Bondarenko.
For a full look at Tuesday's results, click here.