DUBAI, United Arab Emirates — Top-seeded Novak Djokovic advanced to the semifinals of the $2.23 million Dubai Tennis Championship on Thursday with a straight sets win over Marin Cilic, but No. 2 seed Andy Murray withdrew with a viral infection hours before his match.

Third-seeded Gilles Simon of France defeated compatriot Fabrice Santoro 7-6 (3), 6-1, and will next face Djokovic, who defeated Cilic 6-3, 6-4 in 1 hour, 37 minutes.

Murray, ranked No. 4, was scheduled to play the final match of the day on Center Court against France's Richard Gasquet, who will now play fourth-seeded David Ferrer of Spain in the semis.

Ferrer, who beat Igor Andreev of Russia 7-5, 6-1, denied that Murray's withdrawal meant he would now have an easier semifinal.

"No, no. Murray going out doesn't make it any easier for me because Gasquet is a very good player," Ferrer said. "The last time I played against him, it was very tough."

Murray, also bothered by an ankle injury, said he's been feeling poorly since the Australian Open last month.

"I got it first down in Australia, and I haven't been the same really since," Murray said. "I woke up in the middle of the night sweating. I got some anti-viral (medication) from the doctor ... but it didn't help so much."

The Djokovic-Cilic match was perhaps the best match of the tournament so far, with the Serb producing some superb returns to break Cilic of Croatia three times. Cilic, who lost for just the second time this year, failed to convert any of his six break points.

"I was trying in the last three matches to find this exact rhythm, and that's what I finally did today," Djokovic said. "I think the key was movement and focus. I was really trying to move well in the point, be patient, and just wait for the chances, because I was returning very well."

Murray's withdrawal was another blow for an event already hit by controversy and a spate of injury-related absences. Murray is doubtful for Britain's Davis Cup match against Ukraine next week after his doctor advised him to rest for a week to 10 days.

"I don't know. I obviously want to try and play," Murray said. "Ill see how I feel and give it my best shot to get ready."

Earlier, World No. 1 Rafael Nadal and No. 2 Roger Federer withdrew with injuries, while defending champion Andy Roddick declined to defend his title, saying he disagreed with the Emirates' decision to deny Israeli Shahar Peer a visa to play in the women's tournament. Russian world No. 5 Nikolay Davydenko and No. 9 Fernando Verdasco of Spain also opted out.