David Ferrer will face Nicolas Almagro in an all-Spanish quarter-final at the Australian Open after they took contrasting roads to the last eight on Sunday.
Ferrer, the fourth seed in celebrated countryman Rafael Nadal's absence, wore down Japan's Kei Nishikori in straight sets to reach his third straight quarter-final at the year-opening Grand Slam.
But 10th seed Almagro was only on court for over an hour before his Serbian opponent Janko Tipsarevic retired with a foot injury at 6-2, 5-1.
Ferrer, on track to face defending champion Novak Djokovic in the semi-finals, has never lost to Almagro in 12 meetings.
Djokovic was due to face Swiss 15th seed Stanislas Wawrinka in a night match later Sunday on Rod Laver Arena, with the winner to face Czech fifth seed Tomas Berdych in the quarters.
Berdych defeated Kevin Anderson 6-3, 6-2, 7-6 (15/13) in 2hr 44min after surviving a nerve-racking tiebreaker in which the South African had five set points.
Ferrer, who will usurp Nadal as world number four after the Open, was far too consistent and disciplined for 16th seed Nishikori, winning 6-2, 6-1, 6-4 in 2hr 10min, but he dismissed suggestions he was in the top four on merit.
"I am top four because Rafael has been injured a long time. It's true," Ferrer admitted.
"I think the top four, they are better. It's my opinion. But I am trying to win every match. The results, are there, no? I'm not making something up.
"It's very difficult for me to win a Grand Slam because there are the top four. At this time they are better than the other players."
Ferrer was promoted to fourth seed in the year's opening Grand Slam when Nadal pulled out with a stomach virus, after missing all of last year after Wimbledon with a knee injury.
Although Nishikori had beaten Ferrer in their only previous Grand Slam encounter at the 2008 US Open, this time it was clear-cut for the Spaniard.
Nishikori's exit ended Asia's hopes in the men's singles draw as he was bidding to repeat last year's quarter-final appearance in Melbourne.
"He gets every ball, so I have to work 100% on every point and he also return well," Nishikori said of playing Ferrer. "It was hard to hold my serve. Yeah, it's always tough to play against him."
Meanwhile, Almagro said he was disappointed to go through to his first Australian Open quarter-final at the ninth attempt because of Tipsarevic's injury.
"I'm not completely happy because Janko was injured. That's not the way you want to win," he said. "Sometimes you can't do your best and you need to decide to stop if you want to be ready for the next tournament.
"I think he took the best decision if he's really bad.