BARCELONA - World number one Rafael Nadal suffered his first defeat in Barcelona since 2003 on Friday when compatriot Nicolas Almagro ended his 41-match winning run in the Spanish city. Top seed Nadal, the eight-time champion, lost 2-6, 7-6 (7/5), 6-4 to Almagro in a quarter-final lasting 13 minutes short of three hours.Nadal, who lost in the Monte Carlo Masters quarter-finals to David Ferrer last week, had last been beaten in Barcelona when he was just 15 years old. It was 28-year-old Almagro's first win over Nadal in 11 meetings, a series which included a straight sets loss in the 2013 Barcelona final.He needed two match points to secure his shock triumph while surviving 47 unforced errors. The sixth seed had also been a break down in the deciding set. Nadal's last defeat at the tournament was in the second round to compatriot Alex Corretja in 2003 before he skipped the 2004 event through injury. His loss of the second set to Almagro on Friday was the first he had dropped at the Real Club de Tenis since 2008.Almagro, the world number 20, will face either Germany's Philipp Kohlschreiber or Santiago Giraldo of Colombia for a place in Sunday's final. Japan's Kei Nishikori continued his impressive return to action after a three week absence due to a groin injury as he beat 12th seed Marin Cilic 6-1, 6-3 to reach the semi-finals. Nishikori, seeded fourth, was ruthless in the opening set as he broke the big Croat's serve three times. The second set was more of a contest, but the world number 17 still had too much as he sealed victory in just over an hour to register his best ever run in Barcelona. Next up for Nishikori will be a meeting with Latvian Ernests Gulbis after he secured a third semi-final appearance of the season with a 6-1, 6-4 win over Russia's Teimuraz Gabashvili.Meanwhile, defending champion Maria Sharapova marched into the semi-finals of Stuttgart's WTA tournament with a 6-4, 6-3 win over top-seed Agnieszka Radwanska in Friday's quarter-finals. "That was a big win for me," admitted Sharapova after picking up her 11th straight win in Stuttgart where she is bidding for a hat-trick of titles having won the 2012 and 2013 tournaments."That was my biggest win since my comeback from injury," she added having missed four months last year with a shoulder injury. Sharapova claimed her ninth win in 11 matches against world number three Radwanska of Poland, but the statuesque Russian did not have things her own way, despite needing only one hour, 39 minutes to claim victory.After a total of seven breaks at the start of the match, as the momentum swung back and forth, Sharapova finally won her first service game to take control of the first set. "That was one of the key moments," she said after eventually needing eight match points to claim the win. She will now face either Spain's Carla Suarex Navarro or Italy's Sara Errani in Saturday's semi-final."It'll be a tough game, they are both clay-court specialists," said the Russian. Having won all four Grand Slams, Sharapova is bidding to claim a personal landmark this week in Stuttgart by winning a tournament three times in succession. Victory bought an extra bonus for the Russian as failure to beat Radwanska would have seen Sharapova fall out of the top ten for the first time in three years.