Rafael Nadal's Barcelona Open winning streak ended by Nicolás Almagro

Rafael Nadal's quarter-final defeat to Nicolás Almagro was his first Barcelona Open loss since his debut as a 15-year-old in 2003. Photograph: Fotopress/Getty Images

Rafael Nadal's clay-court struggles worsened on Friday as his 41-match winning streak at the Barcelona Open ended with a three-set loss to Nicolás Almagro in the quarter-finals.

Nadal was looking for his ninth title in Barcelona but lost 2-6, 7-6, 6-4 a week after going out in the quarter-finals of the Monte Carlo Masters to David Ferrer. Nadal, widely considered the greatest clay-court player of all time, had not lost in the tournament since his debut as a 15-year-old in 2003, although he did not play in 2010. He had not dropped a set in Barcelona since the 2008 final.

The 20th-ranked Almagro converted his second match point, smashing a forehand down the line for his first career victory over his fellow Spaniard at the 11th attempt. "I had a lot of opportunities in the second set," Nadal said. "I didn't take advantage of break points, so credit goes to him."

After failing to convert any of his five break points in the second set, Nadal missed a return in the tiebreak to give Almagro a 6-5 lead. Almagro followed up with a crosscourt forehand winner to level the match and end Nadal's run of 44 straight sets at the tournament.

Both players were steady on serve until an exchange of breaks made it 4-4 in the third, and Nadal then sent a shot long to be broken again and give Almagro a chance to serve for the match. Nadal set up two straight chances to break back, but hit a forehand long and then sent a smash into the net with Almagro out of position.

Nadal then saved the first match point when Almagro's backhand flew wide. But the underdog used a serve-and-volley to save a third break point of the game before Nadal's long return set up the second match point.

Nadal had not been eliminated this early in back-to-back clay-court tournaments since 2004, when as an 18-year-old he also failed to get past the quarter-finals in Stuttgart and Bastad.

"This is an important win for my career," said Almagro, who celebrated wildly. He will face Santiago Giraldo in Saturday's semi-final after Philipp Kohlschreiber retired with an injury while trailing 6-4, 4-3.

Earlier, Kei Nishikori of Japan and Ernests Gulbis of Latvia overpowered opponents to set up a meeting in the other semi-final. The fourth-seeded Nishikori continued his good run since returning from a groin injury with a 6-1, 6-3 victory over Marin Cilic of Croatia, while the ninth-seeded Gulbis dismissed Teymuraz Gabashvili of Russia 6-1, 6-4. Gulbis saved all five break points against Gabashvili, who had knocked out the fifth-ranked Ferrer.