Updated

Barcelona, Spain (SportsNetwork.com) - For the second time in two weeks, the great Rafael Nadal stunningly lost to a fellow Spaniard in a clay court quarterfinal.

A week after succumbing to David Ferrer at the Monte Carlo Masters, the eight- time Barcelona champion Nadal gave way to capable Nicolas Almagro for the first time in 11 career meetings. Almagro was last year's Barcelona runner-up to Nadal.

A sixth-seeded Almagro halted a 10-match losing streak at the hands of Nadal with an unexpected 2-6, 7-6 (7-5), 6-4 decision Friday at the $2.55 million Barcelona Open.

An elated Almagro prevailed in 2 hours, 47 minutes, as he converted on his second match point by firing one final forehand winner past a struggling Nadal at Royal Barcelona Tennis Club.

After titling in Rio de Janeiro in February, the clay court king Nadal has now failed to title on his favorite surface in his last two events and lost two of his last four matches on his beloved dirt.

The world No. 1 superstar was the three-time reigning champ in Barcelona, where he was riding a 41-match winning streak.

Nadal, who has now failed to title in his last four tournaments, is still the reigning French and U.S. Open champion and was this year's Australian Open runner-up to Swiss Stan Wawrinka.

"I started the season OK except for some lack of confidence and competitiveness in important moments of certain matches," he said.

Almagro was a clay court runner-up in Houston two weeks ago. His semifinal opponent on Saturday will be Colombian Santiago Giraldo.

Also on Friday, fourth-seeded Japanese Kei Nishikori whipped 12th-seeded Croat Marin Cilic 6-1, 6-3, ninth-seeded Latvian Ernests Gulbis dropped Russian Teymuraz Gabashvili 6-1, 6-4, and Giraldo knocked out 10th-seeded Philipp Kohlschreiber 6-4, 4-3, as the German retired on Day 5. The highest-remaining seed Nishikori will face Gulbis in the other semi.

This week's winner will earn $580,000.