It's raw power and 15 Grand Slam titles against consistency and one Grand Slam final defeat in the French Open semifinals on Thursday when Serena Williams goes up against Sara Errani.

On the face of it there should be only one winner - which would put the 31-year-old American into Saturday's championship match, with Maria Sharapova and Victoria Azarenka looming in the other half of the draw.

Williams has been on a mission in Paris - determined and fully focussed for once on vanquishing the demons that have bedeviled her at Roland Garros for the last 11 years since her first, and to date, only French Open title.

Four rounds for the loss of just 10 games, under the watchful eye of new French coach Patrick Mouratoglou, brought her career best winning streak to 28 and she opened her quarterfinal against Svetlana Kuznetsova in similar fashion with a 6-1 first set romp.

But, out of the blue, Williams got the Paris blues again as she surrendered the second set and looked in a panic as she faced break points on her serve to fall 0-3 down in the third.

But this time she rallied to see off the Russian by winning six out of the next seven games to set up a semifinal against a player she has opposed five times for the loss of just one set.

Straight-forward enough on the face of it, but Williams is wary of a player who rarely, if ever, disappoints on the claycourts, having reached the final in Paris last year before losing to Sharapova.

"It's going to be a really good match," the top seed said.

"You've got to appreciate how consistent she is. We had a pretty tough match in Madrid (7-5, 6-2 last month). I'm going to be ready.

"I'm glad I played her in Madrid because I know she's here to play and she's here to compete. She's so serious. I can be ready for that."

Errani, at 1.64 meters and 60 kilograms an Italian lightweight in a world of towering young women, will rely on her work ethic, claycourt expertise and mental fortitude to try to make a match out if it.

She showed all those qualities in defeating fourth seed Agnieszka Radwanska of Poland 6-4, 7-6 (6) in the quarterfinals and she is fully prepared for a David against Goliath showdown on Thursday.

"For sure it will be very difficult because she's very strong," she said.

"Physically, she's an incredible athlete, so is not easy to play against her because of this because she has a lot of power.

"So it will be tough, but maybe on clay is a bit better(for me) than the other surfaces. But very tough."

(China Daily 06/06/2013 page24)