Serena Williams bombshell pregnancy announcement last month triggered a sequence of events that has left this years womens draw at Roland Garros wide open and primed for a new champion.

The 23-time Grand Slam winner learned she was pregnant just two days before starting a successful assault on January's Australian Open and won't return before next year.

The French federation then refused to award Maria Sharapova a wild card for the tournament with the Russian on the comeback trail following a 15-month doping suspension.

"While wild cards can be awarded to players returning from injury, this cannot be the case for those coming back from doping bans," FFT president Bernard Guidicelli said last week when announcing the decision.

With Li Na long since retired that means the winners of five of the past six French Opens -- Williams (2013, 2015), Sharapova (2012, 2014) and Li (2011) -- are absent from the field, while several pretenders to the Coupe Suzanne Lenglen are battling injury and loss of form.

Simona Halep, the 2014 runner-up, established herself as arguably the leading challenger by winning the Madrid Open before reaching the Rome final, but an ankle injury has cast doubt over her status.

"Arriving early in Paris for treatment," Halep said in an Instagram post on Wednesday. "The MRI scan shows a torn ligament from the fall in Roma. I'm keeping my fingers crossed for RG and will do everything possible to be ready.

"Doctors say it's 50/50 at the moment but it's made good improvement since Sunday... We are remaining very positive."

World number one Angelique Kerber has endured a miserable clay-court season, losing early in Stuttgart and crashing out in her Rome opener, while retiring from her last-16 clash in Madrid with a lower back injury.

Defending champion Garbine Muguruza's fortunes on the surface have proved almost as bleak.

Her only three wins came in Rome where she reached the semi-finals only for a neck injury to force her to quit against eventual champion Elina Svitolina, the fourth time the Spaniard has failed to complete a match in 2017.

'No favourite'

Victoria Azarenka, the 2012 and 2013 Australian Open champion, hasn't played since last year's Roland Garros after the birth of her son.

While the 27-year-old recently said she is "ready to start competing", her return is scheduled for next month's grass-court tournament in Mallorca as a tune-up ahead of Wimbledon.

Denmark's Caroline Wozniacki suffered a scare when she limped out of her first-round match in Strasbourg on Monday with a back problem, while third-ranked Karolina Pliskova's best results this season have come on hard courts.

Svitolina climbed to a career high of sixth after landing her fourth title of the season at the Italian Open, but the Ukrainian remained coy on her chances.

"There is no one I can name as a favourite," she said, with Svitolina's run to the 2015 Roland Garros quarter-finals the only time she has advanced to the second week at a major.

Meanwhile Italy's Sara Errani, the 2012 finalist, has tumbled down the rankings and must come through three rounds of qualifying just to reach the main draw.

Petra Kvitova could provide one of the tournament's feel-good storylines though with the two-time Wimbledon champion in line for a shock comeback in the French capital.

The former world number two has been sidelined since December after suffering career-threatening injuries to her left hand while fighting off a knife-wielding intruder at her home the eastern Czech town of Prostejov.

"Hi guys, I have some news. I will be flying to Roland Garros this evening (Wednesday) and taking part in a press conference on site at 2:30pm local time on Friday," Kvitova wrote on social media.

"Keep everything crossed for me that I will be able to play there!"