Malaysian Open organisers confirmed on Friday that defending champion Mikhail Youzhny and top seed Tomas Berdych have pulled out of this year's event.
Youzhny, who has been suffering from a chronic back injury, will now not take part in the tournament which begins with qualifying rounds Saturday and ends October 2 at the Putra Stadium in Malaysia's capital Kuala Lumpur.
He played an extended Davis Cup match last week and that did not help his back. Youzhny needed five hours to beat Thomaz Bellucci, in a result which kept his country in the elite Davis Cup group.
Youzhny, 29, who reached as high as number eight in the ATP world rankings but is now at 32nd, has had a stop-start year due to the injuries and has yet to win a title.
"I have to take care about my back and that means I have to have some special treatment in Moscow," Youzhny said.
"It is because of that I cannot make the trip to Kuala Lumpur. This is a tournament I like very much and last year was very successful for me," he added.
Berdych also has been troubled with a shoulder injury for the past few weeks and it was this injury that prompted him to retire from his match in the third round of the US Open while playing Janko Tipsarevic.
"I am really sorry I cannot make it to Kuala Lumpur this year. I have had some good results there before and I really like the city and the people," he said.
"I was really looking forward to being there again but my shoulder is still troubling me... I hope I can try and come back next year," Berdych added.
Tournament director Nick Freyer said they were disappointed not to have the two top players but "are 100 percent ready to roll in all areas and the show must go on."
Meanwhile, 2009 champion Nikolay Davydenko is returning in the hope of regaining his title.
Davydenko, who was knocked out of the recent US Open by world number one Novak Djokovic, has already pocketed one title in 2011, winning the BMW Open to maintain his record of winning at least one ATP title for the past nine years.
Spain's Nicolas Almagro, who is ranked 12th, will be the second seed. The full list of names and the draw for the third Malaysian Open will be announced on Saturday.