Rafael Nadal was tested for the first time this week as he beat Italian Potito Starace 6-2, 7-5 on Friday to reach the semi-finals of the Barcelona Open and extend his record claycourt winning streak to 70 matches.

The top seed was below his best and was pushed hard by the Italian world number 72 before coming through to set up a clash with fifth seed and fellow Spaniard David Ferrer, who ousted Argentine fourth seed David Nalbandian 7-6, 6-2.

"I did not play as well as normal but it was difficult because the wind was swirling and he played well," Nadal said.

"It was a tough match but in the hardest moments, like at 5-5 (in the second set), I managed to overcome my difficulties."

Ferrer has beaten Nadal in the past and although the top seed has won the last three of their four meetings, he said he expected a tough match.

"I think it is one of the most difficult matches because Ferrer is one of the best players on clay-courts," he said.

"He is solid, very fast and for sure it will be my hardest match so far." 

Starace, whose best results have come on clay, forced Nadal into some uncharacteristic errors early on before the Spaniard broke twice to win the opening set.

Nadal, struggling for his usual dominant form, was forced to save a break point in the second game of the second set and two more in the eighth game.

When the Spaniard broke to lead 5-4 it looked over but a sloppy game allowed the Italian to level at 5-5.

However, Nadal then broke the Italian again and this time served out for victory and a place in the last four.

Nadal is bidding to become only the second man, after Swede Mats Wilander, to win the tournament in three successive years.

Ferrer reached the last four in Barcelona for the first time as he made it five wins out of six against Nalbandian.

Neither man faced a break point in the opening set but some sloppy play from Nalbandian allowed Ferrer to take the tiebreak 7-5, prompting the Argentine to slam his racket down in disgust.

The loss of the tiebreak seemed to knock Nalbandian's spirit and Ferrer broke serve in the first game of the second set and again in the seventh on his way to his victory.

Argentine 12th seed Guillermo Canas received a walkover into the semi-finals when his opponent, Russian second seed Nikolay Davydenko, withdrew before their match because of a right wrist injury.

Canas, who beat world number one Roger Federer twice on hard courts last month, will play his fellow Argentine, 15th seed Agustin Calleri, who crushed unseeded Spaniard Oscar Hernandez 6-0, 6-3.