Serena Williams will have two obstacles in her path in Saturday's French Open final in Paris -- her opponent Lucie Safarova and a nasty dose of the flu.

The 33-year-old American has much to achieve on the Roland Garros clay courts in the championship match.

A win would be her 20th Grand Slam title, just two shy of the Open-era (since 1968) record of 22 held by Steffi Graf.

It would also put her halfway to achieving the fabled calendar-year Grand Slam of all four titles -- a feat only ever done before by Maureen Connolly (1953), Margaret Court (1970) and Steffi Graf (1988).

On the face of it, Safarova, at 28 playing in her first Grand Slam final, should pose little threat. Williams has won all eight previous matches the two have played.

Still she is wary of the Czech 13th seed who has become something of a late-blossoming talent.

"Lucie has been in great form here, she has beaten some tough opponents and I know she always plays well against me," she said.

"She's a lefty, which always provides different challenges. I know I am going to have to play really well to win.

"But at this point I just want to get better -- it's hard to think about the match or winning another Grand Slam title right now."

The problem, as Williams explained it on Friday after cancelling her practice session and media duties, is a bout of flu that so nearly floored her in her three sets semi-final win over Switzerland's Timea Bacsinszky.

She looked to be heading out of the tournament a set and a break down and clearly in distress with her condition, but on the back of her big serve she hung in and somehow ran off 10 games in a row to move through.

"I've felt really cold so I'm just fighting that, trying to sweat it out. A doctor is coming to see me here at home ... and we'll see if he can do anything else to help, but I don't think there's anything.

"It's just time and obviously I don't have a lot of it but it helps that I can be at my apartment and have my family and friends with me."

"I just have to hope that tomorrow I will be feeling a lot better and be able to give my best on court," she said.

Safarova in contrast was in full swing on Friday winning her doubles semi-final alongside American partner Bethanie Mattek-Sands.

Should the seventh seeds win the title and Safarova takes the singles crown she will be the first player to have done that in Paris since Mary Pierce in 2000.

One of the most popular players on the often heartless WTA circuit, Safarova has a nice-girl reputation, but behind the smiles lies a steely determination.

She knows she has nothing to lose against Williams in what will be the biggest match of her career.

"I have played against her many times, our score is 0-8. But I almost made it past her at the Hopman Cup in January. That was a superb game," she said.

"I was a whisker from a win. Of course she's a legend. On the other hand, she likes clay the least of all surfaces. I have to go for it.

"She doesn't like my left hand, the left-handed rotation, and the body serve. I will definitely try to make her run."

If she wins she will be the first Czech player to win since Hana Mandlikova in 1981 -- achieved before Czechoslovakia split into the Czech Republic and Slovakia.

Her hopes of doing that could well depend on if the rest and therapy can get Williams back to health in time