Paris, France, 28 May 2012 | AAP

West Australian Casey Dellacqua threatened to post the first upset of the French Open on Sunday before eventually going down in the opening round.

Dellacqua, a former women’s doubles finalist at Roland Garros and the reigning mixed doubles champion, led 21st seed Sara Errani by a set and a break on court three.

But she let the big opportunity slip, dropping 11 of the next 13 games to lose 4-6 6-2 6-2.

“Disappointed not to get the win today. It was a tough three-setter against a very tough opponent. But thanks everyone for your support,” the Aussie tweeted after the match.

Errani came into the tournament boasting a tour-best three titles on clay this season.

Dellacqua’s doubles partner at last week’s Brussels Open, compatriot Anastasia Rodionova, also went down fighting in her first round match.

Playing on Roland Garros’s atmospheric “bull-ring” No.1 court, Rodionova twice served for the match in the second set against local Mathilde Johansson, before going down 5-7 7-6(6) 6-4 after three hours .

Little separated the pair on the stats sheet except for in the winners department, which, surprisingly, Rodionova came out on top of by 43-26.

Yet Johansson fed off the rambunctious energy of the Parisian crowd, helping her move through to the second round at Roland Garros for the first time in four years.

Three Australian men open their campaigns on Monday, hoping to join Australia’s sole winner on Sunday, Sam Stosur, in the second round.

Bernard Tomic, the 25th seed, plays Austrian Andreas Haider-Maurer, Lleyton Hewitt takes on Slovenian Blaz Kavcic, and Matthew Ebden faces German 24th seed Philipp Kohlschreiber.