Argentina's Juan Martin del Potro wipes his brow during a practice session in Buenos Aires, Argentina, Wednesday, Sept. 12, 2012. Slowed by an injury to his left wrist, del Potro is expected to play ... more 

Argentina's Juan Martin del Potro wipes his brow during a practice session in Buenos Aires, Argentina, Wednesday, Sept. 12, 2012. Slowed by an injury to his left wrist, del Potro is expected to play when Argentina opens its Davis Cup tennis semifinal against the Czech Republic on Friday. (AP Photo/Natacha Pisarenko) less