Marcos Baghdatis was spurred on by a vocal crowd as he knocked top seed Juan Martin del Potro out of the Sydney International.
The 2010 champion, Baghdatis fought back from a slow start to complete the 7-6 (9-7), 6-4 victory in one hour and 40 minutes.
Del Potro, the last of the seeded players in the men's draw, was clearly agitated by vocal sections of the crowd who were cheering on the popular Cypriot and had a lengthy discussion with court umpire Fergus Murphy at the end of the first set.
It did little good for the giant Argentine, who struggled to deal with Baghdatis' tremendous defensive qualities in the second set.
Baghdatis made the decisive break in the seventh game of the second set, before serving out the match much to the fans' approval.
The 26-year-old says he has enjoyed so much success at the tournament in part because he feels at home - and his grandmother's cooking.
"I have lots of relatives here, my grandma lives here and I just love coming back every year," Baghdatis said.
"My Lebanese food from my grandma makes me feel good."
Del Potro looked in control in the first set, having broken Baghdatis in the seventh game to take a 4-3 lead.
But Baghdatis broke back soon after to make it 5-5, before both players held serve to force a tie-break.
Again del Potro took the early advantage and had two set points, but through brilliant defensive tennis, and with a bit of good fortune from the net, the scrappy Cypriot saved both and not long after only needed one set point of his own to take out the set.
Baghdatis was pleased to have improved from a hard-fought three-set victory over Australian Matthew Ebden in the previous round.
"I played great today, I had a not so good match yesterday in tough conditions and (my coach) just said to go for it and I went for it," he said.
"I was playing really aggressive. It was great."
In other quarter-final action, Finland's Jarkko Nieminen beat American Bobby Reynolds 6-3, 6-3, third seed Richard Gasquet was upset 6-4, 7-6 (7-4) by Denis Istomin, while Julien Benneteau downed Alex Bogomolov Jnr 6-2, 6-4.
AAPTags: tennis, sport, sydney-2000 First posted January 12, 2012 22:56:29