Juan Martin del Potro of Argentina waves after winning over Rhyne Williams of the U.S. in their first round match at the Australian Open tennis championship in Melbourne, Australia, Tuesday, Jan. 14, 2014. (AP Photo/Andrew Brownbill)
Juan Martin del Potro of Argentina makes a backhand return to Rhyne Williams of the U.S. during their first round match at the Australian Open tennis championship in Melbourne, Australia, Tuesday, Jan. 14, 2014. (AP Photo/Andrew Brownbill)
Juan Martin del Potro of Argentina serves to Rhyne Williams of the U.S. during their first round match at the Australian Open tennis championship in Melbourne, Australia, Tuesday, Jan. 14, 2014. (AP Photo/Andrew Brownbill)