In another quarterfinal clash, Russia's Mikhail Youzhny beat Serbian Janko Tipsarevic 6-3, 6-4 to set up a last-four meeting with Melzer on Friday.

With world number one Roger Federer and former US Open champion Andy Roddick withdrawing before the start of the tournament and the early exits of Briton Andy Murray and fellow seeds Nikolay Davydenko, Jo-Wilfried Tsonga and Gilles Simon, the Dubai event has lost its luster.

Melzer, 28, gained swift revenge for his semifinal defeat by Cilic at the Zagreb Indoors earlier this month.

"There were very tough conditions, with hot weather and the balls flying," said Melzer. "I kept my game together after being 4-1 down and then played an almost perfect match." Cilic, 21, was heavy favorite going into the quarterfinal, after winning two tournaments already this year.

The Croatian lost only three points in his opening three service games and went a break up but Melzer saved two break points in his next service game before a wide Cilic forehand gave the left-hander a break back.

"I was hitting the ball well and serving good," said Cilic.

"Then I had a little bit of a rushed game on my serve and I lost three or four points in a row. From there, he started to play better. Melzer deserved it." Cilic had a set point at 7-6 in the tiebreak, but Melzer hit a cross-court winner and went on to take the tiebreak 10-8 with an ace.

Cilic changed to a more aggressive game but was unable to stop the Austrian getting to match point with a forehand winner.

The Croatian then hit a backhand long to end the contest.

Youzhny wrapped up a routine victory over a jaded Tipsarevic, who a day earlier had beaten third seed Murray in three sets.

"I took a little bit advantage of Janko because he had a very tough match last night," said the Russian. "And I finished a little better than him." The world number 15 has been troubled by wrist and hamstring injuries, but he converted two of his three break points to make the last four of the Dubai event for the fourth time.

Meanwhile in Kuala Lumpur, third seed Zheng Jie of China slumped to a 6-2, 6-3 defeat by Taiwan's Chang Kai-chen in the second round of the Malaysian Open on Thursday.

Chang was an unstoppable force and crushed the experienced Zheng with a mix of accurate backhand returns and powerful smashes.

The Taiwanese player dominated the match and booked her quarterfinals berth. Her convincing win was wrapped up in 75 minutes amid some exciting rallies.

"I put pressure on her. I played aggressive to win. I am very happy," she told reporters.

Zheng hailed Chang's attacking style but admitted a controversial line call "affected me a little bit." "She played so fast. I changed my style of game. I tried some lobs and slices but I could not get the points. She played very well," she said.

"I really wanted to win. She (Chang) looked so hungry (for a victory)," Zheng added.

Chang said she would try to beat Austria's sixth seed Sybille Bammer in the quarters Friday.

"I don't get pressured playing against anyone. I just go out and do my best. I will do the right things against her (Bammer)," she said.

Early in the week China's second seed Li Na, a favorite in the tournament, was knocked out in the first round.

Earlier, South Africa's Chanelle Scheepers reached her first WTA quarterfinals when she defeated Tatjana Malek of Germany 4-6, 6-2, 6-3.

Malek gave the 26-year-old, who is the South African No.1, a scare before eventually prevailing in two hours and 27 minutes.

Meanwhile, seventh seed Magdalena Rybarikova of Slovakia defeated wildcard entry Noppawan Lertcheewakarn of Thailand 6-4, 7-5 to reach the last eight, where she will face top seed Elena Dementieva of Russia.

Also through to the last eight is Austria's Bammer who trounced Uzbekistan's Akgul Amanmuradova 6-3, 6-0.