Top seed Novak Djokovic withdrew from the Thailand Open with a back injury, handing the tournament its second blow after world number two Rafael Nadal earlier also pulled out.
The world number three failed to arrive in Bangkok for the event which started on Tuesday, after leading Serbia to Davis Cup victory over Australia on the weekend.
ATP officials said the 20-year-old was suffering a back injury, and comes after playing almost nine hours of Davis Cup tennis over three days.
He will be replaced in the draw by Swiss George Bastl.
The loss of the Serb, beaten in the US Open final earlier this month by Roger Federer, comes two days after Nadal was forced to pull out due to continuing tendonitis in his left knee.
World number five Andy Roddick becomes the highest-ranked player in the field here, and opens his campaign as second seed against Taiwan's Wang Yue-Tzuoo.