FILE - In this Jan. 24, 2010, file photo, Juan Martin del Potro of Argentina, waves as he leaves the court  after his loss to Marin Cilic of Croatia in a fourth round match  at the Australian Open tennis championship in Melbourne, Australia. A person familiar with Juan Martin del Potro's plans tells The Associated Press that the 2009 U.S. Open champion will not defend his title at the year's last Grand Slam tournament.  The person spoke to the AP on Saturday, Aug. 21, 2010, on condition of anonymity because an official announcement has not been made. (AP Photo/Andy Wong, File)

Photo by: Andy Wong

FILE - In this Jan. 24, 2010, file photo, Juan Martin del Potro of Argentina, waves as he leaves the court after his loss to Marin Cilic of Croatia in a fourth round match at the Australian Open tennis championship in Melbourne, Australia. A person familiar with Juan Martin del Potro's plans tells The Associated Press that the 2009 U.S. Open champion will not defend his title at the year's last Grand Slam tournament. The person spoke to the AP on Saturday, Aug. 21, 2010, on condition of anonymity because an official announcement has not been made. (AP Photo/Andy Wong, File)