Rome, May 19

Serena Williams withdrew on Saturday prior to the Rome Masters semi-final with China’s Li Na, with the American admitting she just had been feeling small twinges and will be fine for the French Open.

"I’m fine, I’ll be 100% for the French," said 30-year-old Williams, who added she pulled out to make sure she didn’t aggravate the injury.

"I’ve been feeling a little pain this week and I have a huge schedule coming up," said the American who was on a 17-match win streak on clay. China’s eighth seed Li could not have asked for better timing as she heads into her Roland Garros title defence beginning in eight days.

Li will play for the Rome title against German Angelique Kerber or defending champion Maria Sharapova.

Novak Djokovic and Roger Federer will clash for the 25th time in Saturday’s Rome Masters semi-finals while Rafael Nadal also progressed, ensuring the big three all made the last four of this crucial French Open warm-up. Defending champion Djokovic, the top seed, fought through the first set, before racing away in the second to beat French fifth seed Jo-Wilfried Tsonga 7-5, 6-1.

Federer, fresh from his Madrid Masters triumph last weekend, followed the script with a 6-1, 6-2 demolition of Italian Andreas Seppi in just 53 minutes, with the Swiss third seed winning 14 of the first 15 points.

Second seed Nadal, meanwhile, got the better of Czech seventh seed Tomas Berdych, grinding out a 6-4, 7-5 win and will meet fellow Spaniard David Ferrer.

"It was a very good match for me. From the start I played aggressive," said Federer.

"The goals have to be the same against Djokovic -- take it to him and play my game."

Rome is one of the few big events Federer has not won, losing finals in 2003 and 2006.

But the Swiss star, who hasn’t played Djokovic since his marathon US Open semi-final defeat last year, showed his clay game is nearing perfection, just a week before the start of the French Open.