Top seed Andy Roddick has pulled out of this week's Tennis Channel Open in Las Vegas due to weariness.
Roddick, who has played for three successive weeks in the Davis Cup, at San Jose and in Memphis, told tournament director Steve Bellamy he was too tired to play.
"Andy felt bad about it, but he didn't think he had the energy to go the distance here," Bellamy told the Las Vegas Review Journal.
The former U.S. Open champion has been struggling since firing his coach, Dean Goldfine, and hiring his own brother, John, at the beginning of February.
The world number three lost to Romania's Andrei Pavel in the Davis Cup, was upset in the San Jose semi-finals by Britain's Andy Murray, and was shocked in the quarter-finals of Memphis by French qualifier Julien Benneteau.
With Roddick's departure Australian Lleyton Hewitt becomes the top seed in Las Vegas.