Masters Cup champion David Nalbandian entered his fourth straight quarterfinal at the Australian Open with a 6-3, 6-0, 2-6, 6-2 win over Spain's Tommy Robredo on Sunday.
France's Fabrice Santoro, meanwhile, advanced to his first Grand Glam quarter-final with an upset 6-4, 7-5, 7-5 victory over 11th seed David Ferrer of Spain.
The 33-year-old Santoro had not advanced beyond the fourth round at any of his previous 53 Grand Slam tournaments in his 18 years on the ATP tour.
His 54th Grand Slam appearance also makes him joint seventh on the all-time list with Stefan Edberg in the Open era.
The Frenchman is the oldest remaining man in the draw and has appeared in more Australian Opens than any other man who started last Monday.
Fourth seed Nalbandian raced to a two-set lead and looked like he could take the match in straight sets before the 16th-seeded Robredo rallied to take the third set.
Nalbandian found his rhythm again in the fourth set, racing to a 5-2 lead and then sealing a place in the last eight when Robredo hit a backhand into the net on match point.
"I played good today," Nalbandian told reporters. "I'm confident every time I play good .... so I feel much better than at the beginning of the tournament.
"That makes me confident for the second week."
The 24-year-old Argentine, who has yet to win a match in straight sets on his way to the last eight at Melbourne Park, looked on course to do so against Robredo until he allowed the Spaniard a lifeline.
"I think I didn't play at the same level as beginning. Not with the same intensity," he added.
"That's why I think I lost the third set.
"I prefer to win all the matches (easily)," said Nalbandian. I mean, I (have been) playing five and four sets all the time, quite long matches, many, many hours on court.
"But I feel that today I played.... very, very good in the beginning."
Nalbandian's preparations for the year's opening Grand Slam were cut short at the Kooyong invitational tournament due to a stomach virus, but he said he was now starting to feel like his health was improving.
"The doctors told me that every day it goes on it's gonna be better.
"So I feel much, much better than the beginning."
