Rafael Nadal eased into the last eight with a 6-2, 6-3 win over Mikhail Youzhny at the Madrid Masters on Thursday and will next face either Tommy Haas of Germany or Spanish compatriot David Ferrer.
The 26-year-old Nadal now stands at 28-2 on the season as he looks to reach his seventh final since his comeback from a seven-month injury lay-off in February.
"Since I've been back I haven't had the security that I am in my perfect moment or that I can give myself definite goals," said Nadal.
"I just to have try and feel that I am getting better and better day after day.
"I have to have my feet on the ground. I've made it to the quarter-finals of Madrid, which, for me, it's lovely to be able to say that today.
"I'll try to enjoy the quarter-final match tomorrow."
Andy Murray also progressed but had to come through a gruelling three hour battle with Gilles Simon before advancing 2-6, 6-4, 7-6(8-6) to set up a meeting with sixth seed Tomas Berdych who was victorious over Kevin Anderson 7-6 (7/5), 7-5.
It was one round too far for Novak Djokovic's conquerer Grigor Dimitrov though as he was beaten 3-6, 6-4, 6-1 by Stanislaw Wawrinka.
On the women's side, world number one Serena Williams eased into the last eight as she dismantled 13th seed Maria Kirilenko 6-3, 6-1 in just an hour and four minutes.
Williams didn't even face a break point during the match as she steamrollered the Russian, and now faces Spaniard Anabel Medina Garringues in the last eight.
Williams is unbeaten on clay in eight matches so far this season, but after a similarly positive start to last season on the clay was followed by a shocking loss in the first round of the French Open, she says she has learned not to get overconfident ahead of Paris.
"I think more than anything I learned not to become over-confident," she said.
"I think I was a little confident last year and I felt really good; this year I'm going to take every moment like it's my last."
World number two Maria Sharapova, who has yet to drop a set, also continued her stroll into the quarter-finals as she overcame Sabine Lisicki 6-2, 7-5.
The reigning French Open champion said she feels more comfortable than she ever has on clay.
"I think when you win a Grand Slam on a surface, it would be pretty mean of me to say that I'm not comfortable on the surface," she said.
"It took me many years to get to the level of where I am today. It certainly didn't happen overnight."
The Russian, who could overtake Williams at the top of the rankings should she win the title, next faces Estonian Kaia Kanepi.