|Wozniacki, who has dropped to No. 9 in the rankings, hasn't won a title yet this year. (Getty Images)|
The former top-ranked Dane argued several line calls in the match, including a ball that was judged to have hit the baseline early in the second set.
"It's a disgrace that mistakes like this are made," Wozniacki said. "It wasn't even like, 'Could have been in, could have been out.' It was clearly out."
The call came at 1-1 in the second set with Kanepi holding a break point. Wozniacki got to the ball in question, but her shot went out.
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She then argued with chair umpire Poncho Ayala, who agreed with the original call that the ball hit the line.
"How can you sit there and be so arrogant?" Wozniacki said to Ayala. "Have you gone to school?"
After coming back to win the second set, Wozniacki again argued a line call in the third.
Kanepi, who finally won on her fifth match point despite being broken four times while serving for the match, said she wasn't affected by the uproar.
"Well, I think that those things happen in tennis matches, so it's OK if she wants to argue," Kanepi said. "I have to be ready for that and take it easy."
Wozniacki finished the last two years as the top-ranked player but has never won a Grand Slam title. Her best result at a major tournament was a runner-up finish at the 2009 U.S. Open.
The Dane has dropped to No. 9 in the rankings and has not won a title yet this year. She recently hired 2002 Australian Open champion Thomas Johansson as coach.
On the men's side, Rafael Nadal won yet another match at the French Open, improving his record at the clay-court tournament to 48-1.
The second-seeded Spaniard beat Eduardo Schwank of Argentina 6-1, 6-3, 6-4 Saturday in the third round. Nadal has lost only 17 games in nine sets at this year's tournament.
Nadal has won the French Open title six times, and one more will break the record he shares with Bjorn Borg.
The women's defending champion, Li Na, also moved on Saturday, but needed three sets to stop American Christina McHale.
The seventh-seeded Li, who last year became the first Chinese player to win a Grand Slam singles title, rallied to beat McHale 3-6, 6-2, 6-1.
Li committed 44 unforced errors in the match, 20 more than her unseeded opponent.
The last woman to successfully defend her title at Roland Garros was Justine Henin, who won three straight from 2005-07.
Murray, who complained of a bad back in his second-round win over Jarkko Nieminen, showed no ill effects during a 2 hour, 2 minute win in which he never lost his serve and faced break point only once.
"In the next round, it starts from 0-0. Whoever you're playing, you have to go and try and do the same thing," Sharapova said. "There are a lot more rounds to go. It just gets tougher from this point."
Also Saturday, 2010 French Open champion Francesca Schiavone was upset by Varvara Lepchenko of the United States 3-6, 6-3, 8-6, and fourth-seeded Petra Kvitova defeated Nina Bratchikova of Russia 6-2, 4-6, 6-1.
Lepchenko, who was born in Uzbekistan but lives in Allentown, Pa., is unseeded at Roland Garros and had never before made it past the second round at any Grand Slam tournament.
Schiavone won her only Grand Slam title at the French Open two years ago. Last year, she lost to Na in the final.
Kvitova is the only player ranked in the top 10 that has not yet reached a final this year. But she missed some tournaments with injury and illness.
"I had already a tough season. After Australia I was really injured and I couldn't play," said Kvitova, who won her first Grand Slam title at last year's Wimbledon. "So I'm happy that I can play right now and I can be healthy and play my tennis again."