Fourth seed Nikolay Davydenko and 10th seed David Nalbandian suffered heavy defeats at the Australian Open.
Davydenko was no match for Youzhny in round four
Juan Carlos Ferrero sent a woeful Nalbandian crashing out with a 6-1 6-2 6-3 win in their third-round match.
Mikhail Youzhny then saw off fellow Russian Davydenko 7-6 (7-2) 6-3 6-1 in a later fourth-round tie.
And France's Jo-Wilfried Tsonga continued the day of shocks by seeing off eighth seed and compatriot Richard Gasquet 6-2 6-7 (5-7) 7-6 (8-6) 6-3.
Number two seed Rafael Nadal had an easy passage into the quarter-finals after Paul-Henri Mathieu retired with Nadal leading 6-4 3-0.
I was trying to be as aggressive as I was before when I was number one
The Spaniard had been in stunning form, landing 92% of his first serves in the opening set, before the Frenchman retired with a left calf injury.
"I was enjoying the match," Nadal said. "I was playing my best tennis since arriving in Australia.
"I'm happy to be in the quarter-final, but not like this way. I will have extra practice tomorrow to make up for my lost match time."
Injury may also have played a part in Nalbandian's demise as he had pulled out of the pre-tournament warm-up in Kooyong with muscle spasms in his back and was completely out of form against Ferrero.
The match, held over from Friday because of rain, was played under the retractable roof of the Rod Laver Arena despite a dry day in Melbourne.
But the conditions were not to blame as Nalbandian dropped his opening service game and lost the first set in just 25 minutes.
The second set was little better for the Argentine, who was again broken at the start as Ferrero took control without ever having to find top form.
And the former French Open champion got the decisive break in game five of the third set before saving the only break point he faced in the match in the following game.
"Right now, I'm trying to go to the court and be very aggressive all the time, be more aggressive than maybe the other guy," said Ferrero.
"I was trying to be as aggressive as I was before when I was number one or reaching my best results. I'm playing good tennis since, I don't know, two months."
Nalbandian shrugged off the defeat: "He played better than me. That's it. Not a big deal.
"It would have been better if I played some more matches (before the Australian Open) but there is nothing that I can do."
Ferrero next plays fifth seed David Ferrer, who progressed with a 6-3 6-3 6-2 win over American Vince Spadea.
Nadal (left) consoles Mathieu after the Frenchman retires with an injury
Ferrer, who swept aside Spadea with plenty to spare, is looking forward to taking on his friend Ferrero next.
"Juan Carlos is my practice partner and I have played many times against him," he said. "He's playing very well.
"He made the final in Auckland and won easy today over Nalbandian. That's not an easy thing to do. We're going to have a very physical game with a lot of rallies."
Friendships were laid aside at the Rod Laver Arena as Tsonga defeated fellow Frenchman Gasquet to reach his first Grand Slam quarter-final.
"It's difficult to play a friend," said Tsonga, who faces Youzhny next.
"You have to separate everything and say, 'OK, we are friends but when we are on the court, it's different, and I need to do my best to beat him', and that was the difficulty."
Youzhny controlled proceedings against Davydenko, who said afterwards: "I had no pressure or power on my side and I could not do anything."
Finland's Jarkko Nieminen, the 24th seed, ended German Philipp Kohlschreiber's good run with a 3-6 7-6 (9-7) 7-6 (11-9) 6-3 victory and meets Rafael Nadal next.