Defending champion Andy Roddick has become the fifth top 10 player to withdraw from next week's Dubai men's tennis championships.
The American, who is playing in the semi-finals of the Memphis championships this weekend, would have to return to the United States after the Dubai tournament for Davis Cup duty against Switzerland.
He joins Rafael Nadal, Roger Federer, Nikolay Davydenko and Fernando Verdasco among the absentees from the almost $4 million event.
Federer, who will also miss the Davis Cup tie against the United States, is concerned about his back, and Nadal is suffering a knee injury but expects to turn out for Spain in their Davis Cup tie against Serbia.
Tournament sponsors Dubai Duty Free say none of the withdrawals appeared to be a result of the recent furore over the refusal to grant Israeli Shahar Peer entry to the United Arab Emirates for the women's championships.