Against the 12th-seeded Almagro, Nadal saved four break points to dominate the match, especially in the last two sets.

"It's a difficult match," he told reporters."You play against the best players of the world and one of the best players of the world on this surface."

Nadal, whose only loss at Roland Garros came at the fourth round in 2009, is bidding to become the first player to win seven French Open titles, moving him out of a tie with Swedish legend Bjorn Borg.

The second seed will in the semifinals meet his countryman David Ferrer, the sixth seed, who outgunned fourth seed Andy Murray of Britain 6-4, 6-7 (3-7), 6-3, 6-2.

"He had his chances and converted them. He's solid and consistent and if you don't convert opportunities against him, the games become longer and the pressure builds on you," said Murray, who had reached the semifinals in the last five Grand Slams.

The other semifinal will be played between top seed Novak Djokovic and third seed Roger Federer.

Wimbledon champion Petra Kvitova came back from one set down to finish off the giant-killing run of Kazakh qualifier Yaroslava Shvedova 3-6 6-2 6-4 and reach her first time ever French Open semifinals.

Doubles specialist Shvedova looked on her way to the semifinals after she won the first set.

But the Czech fourth seed kept her focus through driving rain to complete victory after her 142nd-ranked opponent drilled a backhand wide on matchpoint.

"I expected it would be tough match and it was actually," said Kvitova.

"She started well and I was very nervous from the beginning making easy mistakes. Then I knew I had to change my game and I had to be the aggressive one and going for the points," she said.

Shvedova said she was worn down by tiredness rather than Kvitova.

"I was just super-tired. In the first set I still had the energy and I played well," she said.

"Then I had just lost energy. The third set is just like I was saying to myself to fight and just try to get all the balls," she added.

Kvitova will next take on title favorite Maria Sharapova for a place in Saturday's final.

Second seed Sharapova beat unheralded Kaia Kanepi of Estonia 6-2, 6-3 to reach the semifinals for the third time.

The Russian took 74 minutes to roll through her 23rd-seeded opponent, making 19 unforced errors and four double faults.

Sharapova expected her clash with Kvitova to be close, but remained confident.

"She's an extremely tough opponent, someone that I have had good success in our last couple of previous meetings," she said.