Nadal, Serena battle through, Sharapova cruises in Madrid
Spanish player Rafael Nadal celebrates his victory at the end of his tennis match against Spanish player David Ferrer at the Madrid Masters at the Caja Magica (Magic Box) sports complex in Madrid on May 10, 2013. Nadal won 4-6, 7-6 (7/3), 6-0.
World number five Nadal pulled off a roller-coaster 4-6, 7-6 (7/3), 6-0 win over world number four Ferrer.
Despite being seeded above Nadal, due to the seven-time French Open winner's seven-month injury lay-off, Ferrer was still left nursing a record of just four wins in their 22 meetings.
"If you don't take your chances against Rafa, you pay a dearly. Against Rafa, Novak, Roger or Murray there's no room for error," admitted Ferrer.
However, the fourth seed didn't seem overawed early on as after both players exchanged early breaks, Ferrer closed out the opening set when a fine crosscourt forehand set up an easy volleyed winner in the 10th game.
Ferrer then looked on course to cause another upset after the surprise defeats of the world's top two, Novak Djokovic and Roger Federer, when he moved 4-2 up in the second.
However, Nadal swiftly broke back to level the set and then took it on the tie-break 7/3.
And there was no stopping the 11-time Grand Slam winner thereafter as he stormed through the third 6-0 to set up a semi-final meeting with Federer's conqueror Kei Nishikori or Pablo Andujar.
In the women's event, Williams and Sharapova stayed on course for a battle for the world number one slot in the final as they progressed into the last four with wins over Anabel Medina Garrigues and Kaia Kanepi respectively.
However, current number one Williams was given a huge scare by 30-year-old wildcard Garrigues before battling through 6-3, 0-6, 7-5.
The American hadn't dropped a set all tournament until the Spaniard romped through the second set and Williams admitted she had to fight to up her intensity levels heading into the decider.
"I think it was definitely a battle. That's the way to describe it. I obviously didn't do much in the second set, and I think I gave her a lot of confidence to play better," said Williams, who conceded a love-set for only the seventh time in her career.
"I wasn't really there. I wasn't really in it. My feet weren't moving. I don't know what happened.
"To turn it around I got up earlier on the changeover and started doing high knees and just stretching and doing anything to try to get my intensity back up where it needed to be."
In an uncharacteristically wild performance, Williams racked up nearly 50 unforced errors throughout the nearly two and a quarter hours of play, and she is determined to start afresh when she faces Sara Errani in the semi-finals on Saturday.
"I definitely want to cut back on my unforced errors. I had a lot of unforced errors today."
There were far fewer problems for Sharapova as she continued her run of not losing a set so far in the Spanish capital with a comfortable 6-2, 6-4 win over world number 51 Kanepi.
"I was just happy to get past the quarter-finals," said Sharapova who goes on to face Ana Ivanovic for a place in the final.
"I feel like I've been stuck in this tournament so it's nice to be in that stage. I felt like I was facing a really good clay court player today. A lot of her success has come on clay.
"I faced her at the French Open where she had really good wins last year, so I know that she's capable and she's playing really well.
"So I was just really determined. I'm happy that I was able to win with that type of scoreline."
Ivanovic sealed her place in the last four with a 6-3, 6-1 win over sixth seed Angelique Kerber, whilst seventh seed Errani ended Ekaterina Makarova's fine tournament, 6-4, 6-3.