SAMANTHA Stosur is bracing for the toughest first-week test of her title credentials when she confronts Russia's Nadia Petrova in the third round of the French Open tonight.
Stosur remains on track for a quarter-final showdown with world No. 1 Victoria Azarenka after a clinical 6-1, 6-4 second-round win over American Irina Falconi.
Petrova, though, is among the small minority of players on tour carrying a winning record over Australia's grand slam champion and the pair have a history of epic encounters on some of the sport's biggest stages.
The powerhouse baseliner lost to Stosur in the longest women's match in US Open history last year - a three-hour, 16-minute third-round heartstopper - before gaining revenge in their most recent meeting, two months ago at Indian Wells.
All up, the one-time world No. 3 leads Stosur 5-2, but they have never squared off on clay.
Now Petrova stands in Stosur's way again after both sauntered through to the last 32 in Paris without dropping a set.
''We seem to run into each other in the third rounds quite often, either at grand slams or the other big tournaments,'' Stosur said.
''I have got to expect another tough one. Obviously, I won the US Open [match] and I lost Indian Wells. She can have a huge serve and she's been at the top of the game before. So you've got to be ready for her to be on - and if she's not, then that's a bonus.''
Stosur has been in ominous touch this week and would be a hot favourite to down American Sloane Stephens or Frenchwoman Mathilde Johansson in the fourth round on Sunday to tee up a likely quarter-final date with Azarenka.
But 2010 runner-up Stosur is reluctant to look beyond Petrova - or compare her form to that of two years ago at Roland Garros.
''It's still only the third round. There's a long way to go before you're holding a trophy or someone is holding the trophy,'' the sixth seed said. ''Two years on, I'm in quite a different stage of my career and I have been through a lot more experiences.'' AAP