(CNN) -- One of the world's leading tennis players has apologized after swearing at members of the crowd at the French Open, having been angered by two people who he said were purposefully trying to put him off.
Janko Tipsarevic, who has dropped outside the top-10 this year, lost his cool halfway through Saturday's defeat by Mikhail Youzhny -- which cost him a place in the last 16 of the season's second grand slam tournament.
"I just snapped, because you could really see they didn't really care what the score was or even who was playing," the Serbian told reporters.
"They just wanted to look nice and be at the French Open. They had no respect to the players in terms of being quiet or whatever.
"So at one point I was getting ready to serve at, I think, 30-15 on my serve and one of the guys just started screaming, calling somebody to the stands."
The duo were reportedly ejected from the stadium, but Tipsarevic said he regretted his actions.
"There is no excuse for my behaviour. I think basically the problem was that I used the F word and that was not pretty. But, on the other hand, I just snapped. It happens to everyone."
Tipsarevic, ranked 12th but seeded eighth for the clay event, lost 6-4 6-4 6-3 to Youzhny as he struggled to recover from Friday's five-set win over Spain's Feliciano Lopez in the third round.
"Youzhny was a much better player from beginning to end," he said. "My feet were just not there. I've not been feeling well for two, three days now, getting half sick, feverish. The match yesterday completely destroyed me."
Youzhny, once ranked as high as eighth but now down 31st, reached the last 16 at Roland Garros for the first time since his quarterfinal effort in 2010.
The 30-year-old Russian will next face 35-year-old German Tommy Haas, who needed 13 match points before finally overcoming American John Isner 7-5 7-6 (7-4) 4-6 6-7 (10-12) 10-8 in a match lasting four hours 37 minutes.
Meanwhile, world No. 1 Novak Djokovic and defending champion Rafael Nadal remain on course for a semifinal showdown.
Nadal, seeking to become the first man to win a grand slam eight times, again had a slow start against fired-up Italian Fabio Fognini but prevailed 7-6 (7-5) 6-4 6-4 for his first straight-sets win this week.
The Spaniard, who complained Friday about the tournament scheduling that had given his opponent extra rest time, will next face world No. 15 Kei Nishikori.
The 23-year-old became the first Japanese male to reach the last 16 at Roland Garros since 1938 as he beat home player Benoit Paire 6-3 6-7 (3-7) 6-4 6-1.
The Frenchman criticized the chair umpire after being docked a point for receiving coaching when on the verge on clinching the second set.
"They would never do this to the top-five players. They would never issue a warning and apply a penalty point, because they know full well that you just can't do that type of thing," Paire said.
Djokovic, seeking to win the only grand slam that has eluded him, brushed off the challenge of Grigor Dimitrov as he beat Bulgaria's rising star 6-2 6-2 6-3.
It came on the day that the Serbian tennis federation announced the death of the woman who discovered Djokovic as a six-year-old boy and coached him until he was 11.
Jelena Gencic, who also worked with grand slam champions Monica Seles and Goran Ivanisevic, was 77 when she passed away.
Djokovic, who became the 40th player on the ATP Tour to register 500 career match wins, will next play German 16th seed Phillipp Kohlschreiber as he seeks to improve on last year's final defeat to Nadal.
World No. 9 Richard Gasquet kept alive France's hopes of a first men's title in 30 years, beating Russia's Nikolay Davydenko 6-4 6-4 6-3 to earn a last-16 clash with Swiss ninth seed Stanislas Wawrinka.
In the women's draw, world No. 2 Maria Sharapova and third-ranked Victoria Azarenka reached the last 16 despite struggling with their serves.
Defending champion Sharapova rallied from 4-1 down in the second set against Zheng Jie to beat China's world No. 43 6-1 7-5 despite making 34 unforced errors in a match featuring 11 breaks of serve.
The Russian will next play 20-year-old American Sloane Stephens, who reached the fourth round for the second successive season with a three-set victory over New Zealand's Marina Erakovic.
Stephens, who reached the semifinals of the Australian Open in January for her best career result, lost in straight sets to Sharapova in Rome last month.
Former world No. 1 Azarenka beat France's Alize Cornet 4-6 6-3 6-1 despite dropping serve six times.
"If I can win that match serving like this, that's pretty remarkable," said the Belorussian, who will next face 2010 champion Francesca Schiavone.
The Italian, also the 2011 runner-up but now dropped to 50th in the rankings, crushed French 13th seed Marion Bartoli 6-2 6-1.
The U.S. will have four women in the fourth round of a grand slam for the first time since 2004 after Jamie Hampton and Bethanie Mattek-Sands joined world No. 1 Serena Williams and Stephens.
Hampton, ranked 54th, upset Czech seventh seed Petra Kvitova 6-1 7-6 (9-7) to earn a clash with Serbia's former world No. 1 Jelena Jankovic -- who eliminated Australia's 2010 runner-up Sam Stosur despite losing the first set.
Mattek-Sands followed up her win over China's 2011 champion Li Na by beating Argentine qualifier Paula Ormaechea 4-6 6-1 6-3 to reach the last 16 for the first time, equaling her best showing in a grand slam.
The 28-year-old will next play Russian 12th seed Maria Kirilenko, who beat Switzerland's Stefanie Voegele 7-6 (7-3) 7-5.