Fourth seed David Ferrer cruised past Kei Nishikori with what he described as "one of the best matches of my career at the Australian Open".
Nishikori, the 16th seed, offered little threat to the Spaniard who won 6-2 6-1 6-4 in two hours and 10 minutes to advance to his third successive quarter-final in Melbourne.
Ferrer broke twice in each of the first two sets to set up a comfortable win. The third was wild as Nishikori started to go for broke but, hampered by a knee injury, he failed to seriously threaten Ferrer's chances of victory.
The fourth seed said: "It was a tough match but in the first two sets I didn't make any mistakes. I played very well, it was one of the best matches of my career at the Australian Open. I'm happy with my game."
His run this week means Ferrer will move into the top four of the world rankings but the modest 30-year-old admits he is some way behind established quartet Novak Djokovic, Roger Federer, Andy Murray and the injured Rafael Nadal.
He added: "I am only in the top four because Rafa has been injured for a long time. That is the truth. I think the top four, they are better (than me)."
Ferrer will take on another Spaniard, Nicolas Almagro, in the last eight after he advanced when Janko Tipsarevic had to withdraw through injury. Serbian Tipsarevic won his previous two matches - against Lukas Lacko and Julien Benneteau - in five sets but was trailing 6-2 5-1 when he pulled out with a jarred heel.
Almagro said: "That's not the way you want to win. But that's sport. Sometimes you can't do your best and you need to stop. I think he made the best decision."
Almagro, seeded number 10, has lost all 12 of his previous matches with Ferrer but is hoping to buck that trend and reach his first grand slam semi-final.
"It will be a good fight. I know him and he knows me," he said. "It is a big opportunity for me to be in a semi-final. I'm ready to fight. I'm healthy and happy with my tennis. I think I'm playing really well and we'll see what will happen on Tuesday."