Can Serena Williams win major number 20?

Serena Williams is looking to her third French Open title. Photo / AP

Serena Williams enters the French Open with tennis legend Martina Navratilova predicting the raging title favourite will chalk up major number 20 and maybe even catch Margaret Smith's all-time grand slam record.

Tackling the elephant in the room, Navratilova says it's inevitable Williams will continue adding to her growing trophy haul and "possibly" surpass Smith Court's benchmark 25 majors as the world No.1 plots a rare calendar-year slam in 2015.

Williams topped Navratilova and fellow American Chris Evert's 18 grand slam singles crowns with a sixth Australian Open triumph in January and is desperate to atone for a shock first-round loss in Paris last year to Garbine Muguruza.

"I want to win Roland Garros," Williams said. No ifs, no buts.

"I've had an opportunity five times to do a career grand slam and I've never done that."

If she does reign for a third time in Paris, Williams will be halfway towards that elusive calendar-year slam, three quarters into a second Serena Slam and just two shy of Steffi Graf's open-era record of 22 majors.

"Serena is amazing, and she will get to 20 slams for sure," Navratilova told the Tennis Podcast ahead of Sunday's start to the claycourt slam.

"She put her career into another gear three years ago after that (first-round) loss to Virginie Razzano at the French Open.

"She really focused herself on the sport. She realised that her time was running out and that if she wanted to make her mark on the sport, she had better get going.

"She has barely lost any matches since."

Not even on clay, supposedly her least preferred surface.

In an extraordinary turnaround after years of modest returns on dirt, Williams won 36 of 37 matches on clay in 2013 and 2014 before her loss to Muguruza and she's carried the form into this season.

With an 8-1 record on clay, Williams is not only a hot favourite in Paris but also playing some of the finest tennis of her life.

The 33-year-old enjoyed her best start to a season in more than a decade, a 25-match winning streak reminiscent of when she last held all four grand slam titles simultaneously back in 2003.

Navratilova says while eclipsing Smith Court's 25 slams remains a tall order, Williams' lack of genuine rivals means it's not out of the question.

Her closest challenger, world No.2 Maria Sharapova, hasn't beaten Williams in 11 years and has lost their past 16 meetings, including the 2013 French Open final.

"The new generation hasn't quite caught up to Serena so she has a nice window there," Navratilova said.

"So it is possible that she will pass Margaret Court."

As at the Australian Open, where Williams prevailed over the Russian once more in the final, Sharapova again looms as the top seed's biggest threat in Paris.

Sharapova round out her preparations with victory in Rome last weekend and has won 20 of her past 21 matches at Roland Garros.

But finding a way of stopping Williams has proven mission impossible for Sharapova since she ambushed the American as a teenager in the 2004 Wimbledon decider.

-AAP