Juan Martin del Potro showed few signs of being slowed by an injured left wrist as he beat Radek Stepanek 6-4, 6-4, 6-2 on Friday to give Argentina a 1-0 lead against the Czech Republic in their Davis Cup semifinal.
Del Potro, who was told by doctors not to play with the inflamed wrist, broke the Czech in the ninth game en route to winning the first set.
The former U.S. Open champion broke Stepanek twice in the second and third set and got stronger as the match went on.
Stepanek tried to work to Del Potro's backhand - where the Argentine uses his left hand - to little advantage on the outdoor red clay.
No. 1 Czech Tomas Berdych faces Juan Monaco in second singles on Friday.