Novak Djokovic extended his perfect start to the season at the French Open on Saturday, beating Juan Martin del Potro 6-3, 3-6, 6-3, 6-2 for his 40th straight victory this year.

Djokovic, who has not lost in 42 matches dating back to last year’s Davis Cup final, returned to Court Suzanne Lenglen on Saturday after splitting the opening two sets on Friday - before the match was suspended because of darkness.

But the second-seeded Serb had no problems on day 2 against Del Potro. He had 41 winners to Del Potro’s 22 and had four of his five breaks in the final two sets.

“I knew before we played this match that it’s going to be a definitely difficult opponent to beat, a player who can equally play well on different surfaces,” Djokovic said. “I was managing to control my game a little bit better today than I did yesterday. I think that resulted with the win.”

Rafael Nadal also appeared to put his struggles behind him, advancing to the fourth round with a 6-1, 6-3, 6-0 win over Croatian qualifier Antonio Veic. Australian Open runners-up Andy Murray and Li Na also advanced, as did three-time Grand Slam champion Maria Sharapova.

“Today he’s done much better than me and he took his opportunities and made the match very difficult,” Del Potro said. “I had my chance in third set, 2-all, two break points, and I miss it. Against this player, if you don’t take your chance, you lose.”

In the next round, Djokovic will face No. 13 Richard Gasquet. The Frenchman advanced to the fourth round with a victory on Friday.

Nadal, Murray, Sharapova advance

Nadal, who needed five sets to win his opening match at Roland Garros, had only 18 unforced errors and managed to break his opponent nine times.

“I did a few things much better than the previous days. Happy for that,” Nadal said. “Just the beginning of the second, for moments of the second set, I had a few more mistakes. But for the rest of the match, I think I started to have better control of the ball.”

Murray moved into the next round despite an injury scare in the second set when he twisted his right ankle. He eventually beat Michael Berrer 6-2, 6-3, 6-2.

The fourth-seeded Brit called for a trainer and had his ankle taped before returning to the court and breaking his German opponent on the next point.

“I just rolled my ankle, and then, obviously, pretty sore for the rest of the match,” said Murray, adding that he would decide later if he can play in the next round. “I’ve just got to wait and see how it pulls up or do all the right things to make sure, give it my best possible shot for the next match.”

Berrer, however, said he failed to take advantage of the situation. “That was a very big chance. I think a chance like this you get maybe once in your life,” Berrer said. “I should have hurt him when he’s down, but that’s difficult for me.”

Murray will next face Victor Troicki of Serbia, who beat No. 21 Alexandr Dolgopolov of Ukraine 6-4, 3-6, 6-3, 6-4.

Also, No. 18 Gilles Simon eliminated Mardy Fish of the United States 6-3, 6-4, 6-2, Juan Ignacio Chela of Argentina defeated Lukas Rosol of the Czech Republic 6-2, 6-4, 3-6, 7-6 (5) and Alejandro Falla of Colombia beat Lukasz Kubot of Poland 6-7 (4), 6-4, 7-5, 6-4.

Sharapova moved into the fourth round by beating Yung-Jan Chan of Taiwan 6-2, 6-3. The seventh-seeded Sharapova overpowered her opponent on centre court, never seriously being threatened throughout the match.

The sixth-seeded Li, who this year became the first Chinese player to get to the final at a major tournament, defeated Sorana Cirstea of Romania 6-2, 6-2 and will next face No. 9 Petra Kvitova. Li has made at least the quarterfinals at the other three Grand Slam tournaments, but she has never progressed past the fourth round at Roland Garros.

Kvitova defeated Vania King of the United States 6-4, 6-2, while Ekaterina Makarova of Russia eliminated No. 16 Kaia Kanepi of Estonia 6-4, 7-5, No. 15 Andrea Petkovic of Germany beat No. 24 Jarmila Gajdosova of Australia 6-2, 4-6, 6-3 and No. 12 Agnieszka Radwanska of Poland defeated No. 21 Yanina Wickmayer of Belgium 6-4, 6-4.

Fourth-seeded Victoria Azarenka of Belarus also advanced, beating No. 30 Roberta Vinci of Italy 6-3, 6-2. “I think I can improve, and I have been improving from match to match, which is important,” Azarenka said. “Probably could do things better, but I have time to work on and prepare for the next match.”

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