(CNN) -- World number one's Rafael Nadal and Serena Williams continued their successful title defenses in Madrid Thursday but the Spanish capital again proved a less than happy hunting ground for Wimbledon champion Andy Murray.
His 2014 travails continued with a 6-3 6-2 defeat to in-form Colombian Santiago Giraldo in the third round, extending his poor record at the Caja Magica since the tournament switched from hard courts to clay in 2009.
Murray scored an impressive victory over Spain's Nicolas Almagro the previous evening, but he never looked set to stage a repeat against Giraldo.
The British No.1 has slipped to eighth in the rankings after undergoing back surgery in the autumn of 2013 and his match against Almagro was his first in a month.
Murray is also without a coach following the end of his relationship with Ivan Lendl, but even at his best might have struggled to cope with Giraldo, who reached the final in Barcelona two weeks ago.
"It's tough because some days just now I'm playing well and then the next day I'm not playing well at all," Murray told gathered reporters after his defeat.
"Even within matches I'm playing really well for periods and then other times not great at all.
"I need to become more consistent," he added.
After losing the opener, Murray had a break point on his opponent's service in the second set but squandered the opportunity before sliding to defeat. In seven tournaments this year, Murray has failed to reach a final and admitted he was struggling to find answers.
"I'm not 100 percent sure what it is, but I need to sit down and think about that over the next couple of days and see what I need to do."
Giraldo will play Spain's Roberto Bautista Agut in the last eight.
Earlier, Nadal, looking to get back to his invincible best after defeats David Ferrer and Almagro in the quarterfinals in Monte Carlo and Barcelona, dispatched Finn Jarkko Nieminen 6-1 6-4.
Nadal saw his 3-1 lead in the second set disappear, but he reasserted his control to go through in some style.
"During the first hour I played better than yesterday, more dynamically and with more intensity," Nadal told the official ATP Tour website.
"I was defending properly and knowing what was happening in every single moment. Perhaps that's something I wasn't able to do in recent weeks," he added.
Nadal will next face sixth seed Tomas Berdych, who had to battle past Bulgarian Grigor Dimitrov 3-6 6-3 6-2 in one hour and 50 minutes.
It was his first win in three meetings with Dimitrov, the turning point in the second set when he broke him for the first of three times.
"Grigor started really well. He was serving exceptionally well, playing aggressively and I couldn't find a way to get into his service games," said Berdych.
"But, finally, I took my first break point in the second set and from that point things changed quite dramatically. I was happy with the way I handled the match and how I played."
Barcelona winner, 10th seed Kei Nishikori also advanced to the last eight with a 7-6 7-6 win over Milos Raonic of Canada.
The Japanese star came from 2-5 down in the first set to win the opening tiebreak and set him on his way to a crucial victory.
"I'm playing well and feeling very confident," said the 24-year-old.
In the WTA event at the same venue, top-ranked Williams overcame problems on her own service in beating Spain's Carla Suarez Navarro 6-2 6-3 in search of a third straight title in Madrid.
Williams was broken twice in her opening three service games, but Suarez Navarro was unable to hold on her own delivery.
It was the same in the second set, with Williams broken twice more but she held on to set up a meeting with Petra Kvitova in the last eight.
Kvitova beat fellow Czech Lucie Safarova 6-4 6-3, while second seed Li Na had a more testing morning as she came from a set down to beat 16th seed Sloane Stephens of the United States 2-6 6-3 6-2.
Australian Open champion Li will now face Maria Sharapova for a place in the semifinals after the Russian continued her superb recent form on clay with a 6-4 6-3 win over Australian Samantha Stosur.
Former French Open champion Sharapova is coming off a title success in Stuttgart and used her serve effectively to see off Stosur.