Stosur edges Petrova in three set marathon.

In warm conditions during the evening match on Louis Armstrong Stadium, the hard-hitting duo exchanged breaks to start the match before Stosur held to love in the third game, setting the tone for what would turn out to be the best women's match of the tournament to date and the longest recorded women's match at the US Open in the open era.

Serving for the first set at 5-3, the Queenslander gave away three set points and was eventually broken by Petrova, who had won 4 of their 5 previous encounters.
The resultant tiebreak was won by the Australian despite a moment of frustration when a successful hawk-eye challenge on a late call gave the Russian the point.

The 27 year-old, who landed 48 winners to her opponent's 37, served for the match at 5-4 in and despite turning two break points into two match points, again found herself broken by the powerful Russian 24th seed.

Petrova broke in the third game of the final set to take the lead for the first time but put a forehand into the net, allowing the Australian to level it at 4-4.

Stosur gave away her third match point with a long forehand before an electrifying rally on her fourth match point went Petrova's way.
Putting immense pressure on the Russian, Stosur created a fifth match point which she claimed as Petrova's return sailed into the net.

The upset of the day goes to Flavia Pennetta for dispatching of Russian third seed Maria Sharapova 6-3 3-6 6-4.