AP Photo/Vadim Ghirda

Juan Martin del Potro was hungry at the start of the Olympic tennis tournament.

He recalled Friday that "I was already thinking about the barbecue I would be eating in Tandil," his hometown in Argentina.

See, del Potro was drawn to face top-ranked Novak Djokovic in the first round. And though the Argentine beat Djokovic for bronze in 2012, he's had three left wrist surgeries since, leaving him struggling with his two-handed backhand. He figured to head home early.

Then he upset Djokovic, and won again, and again, and again, battling through the mounting fatigue to somehow reach Saturday's semifinals. After his 7-5. 7-6 (4) victory in the quarters Friday over Roberto Bautista Agut, del Potro burst into tears, just as he did at the end of the Djokovic match.

He recalled that he wept at the 2009 U.S. Open, "but only when I won the tournament."

"Now I almost cry every day," del Potro said. "I don't know how much more my heart can take, or my legs."

Yet his semifinal opponent is facing the same situation: a Grand Slam champion still working his way back into match shape after a left wrist injury whose heart and legs have been tested throughout this tournament. Rafael Nadal played twice Friday, and, yes, after winning gold in the men's doubles final with Spanish teammate Marc Lopez, he cried, too.

AP Photo/Charles Krupa