MASON, Ohio (AP) -Juan Martin del Potro advanced in straight sets to the semifinals of the Western & Southern Open, which was still catching up from the rain.
Del Potro beat France's Jeremy Chardy 6-1, 6-3 in the opening match Friday morning, reaching the tournament's semifinals for the first time. His biggest concern has been a sore left wrist that he'll have examined before the U.S. Open.
The Argentine won the Open in 2009. The right-hander missed most of the 2010 season while recovering from surgery on his right wrist. The doctor who performed that surgery will look at the other one following the tournament in suburban Cincinnati.
"The good thing: I'm not getting worse, so I can play," he said. "But anyway, I want to wait (for) what the doctor says because I have experience on my other wrist."
Del Potro won the bronze medal at the Olympics in London by beating Novak Djokovic, then was knocked out in the first round of the Rogers Cup in Toronto last week. He's still trying to get his game back to a championship level.
"I'm still feeling a little difference between the top players and me," he said. "But I know I'm getting closer very slowly, so that's important. I'm working for that."
He put Chardy on the defensive right away and didn't give him a chance to get into the match. Chardy survived 13 break points, including three match points, before losing on a long return.
Chardy got into the tournament as an injury replacement for John Isner, who has a sore back. He beat Andy Roddick and Andy Murray, becoming the first injury replacement to reach the quarterfinals of an ATP tournament this season.
Rain interfered with two singles matches Thursday night.
Sixth-seeded Caroline Wozniacki was down a set to Russia's Anastasia Pavlyuchenkova when the rains came. Pavlyuchenkova finished off a 6-4, 6-4 win Friday, then had eight hours to rest before playing a quarterfinal match against fourth-seeded Petra Kvitova.
No. 9 Li Na's match against Sweden's Johanna Larsson was postponed before they could take the court Thursday night. Li needed only 64 minutes to win 6-2, 6-2 on Friday morning, leaving her less than seven hours to get ready for her quarterfinal match against top-seeded Agnieszka Radwanska of Poland.