Nadal continues to boss Berdych

Rafael Nadal claimed his 17th straight victory over Tomas Berdych as he continued his clay-court re-emergence by reaching the semi-finals of the Mutua Madrid Open.

Rafael Nadal, pictured, overcame Tomas Berdych 6-4 6-2 (AP)
Rafael Nadal, pictured, overcame Tomas Berdych 6-4 6-2 (AP)

The world number one expressed delight at his 6-4 6-2 victory, and said he believed it marked a significant moment in his bid to bounce back from shock losses in Monte Carlo and Barcelona.

Nadal told atptour.com: "It was a match with a lot of intensity and perhaps it was my toughest match in the tournament.

"I knew I had to go a step forward. I think I did it pretty well. To make the semi-finals for the first time in the clay season here in Madrid is great news for me."

Berdych held his own through the first six games but was crucially broken in the seventh and never managed to regain a foothold as Nadal saved the single break point opportunity that came the sixth seed's way.

Nadal will play compatriot Roberto Bautista Agut in the semi-finals after the world number 45 secured a 6-3 6-4 win over Andy Murray's conqueror Santiago Giraldo.

The 26-year-old has pulled off a series of notable results so far this season and will be hoping for one more when he faces the defending champion.

"I'm really excited for it to be here in Madrid and make it to the semi-finals to play one of the best players in history," said Bautista Agut. "I am very happy with the tennis I'm playing at the moment."

Fifth seed David Ferrer saw off Latvia's Ernests Gulbis 7-6 (7/3) 6-3 to set up a semi-final against Japan's Kei Nishikori, who was a 6-4 6-4 winner over Spanish veteran Feliciano Lopez.

Defending women's champion Serena Williams was forced to pull out of her quarter-final against Petra Kvitova as a precautionary measure due to a left thigh injury.

The withdrawal of Williams, who has landed the title in each of the last two years, handed Kvitova a walkover into the semi-finals, where she will face Romania's Simona Halep.

With just over two weeks until the start of the French Open on May 25, Williams was determined she should not put her place at Roland Garros at any further risk by allowing the problem to worsen.

She said on the tournament website: "I have an injury in my left thigh, and unfortunately I'll have to retire from this year's Mutua Madrid Open.

"I suffered it during my first-round match. I started to feel better but it is important that I have enough time to rest and recover."

Halep eased past Ana Ivanovic 6-2 6-2 in exactly one hour.

Maria Sharapova came through a gruelling two-and-a-half hour battle against second seed Li Na, winning 2-6 7-6 (7/5) 6-3, and will play third seed Agnieszka Radwanska, who beat French qualifier Caroline Garcia 6-4 4-6 6-4.