PARIS — 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 consecutive victory this year.
Djokovic has not lost in 42 matches dating to last year's Davis Cup final. He and Del Potro returned to Court Suzanne Lenglen on Saturday after splitting the first two sets Friday before the match was suspended because of darkness.
The second-seeded Serb had no problems on Day 2 against Del Potro, the 2009 U.S. Open champion. 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 victory over Antonio Veic. Australian Open runners-up Andy Murray and Li Na also advanced, as did three-time Grand Slam champion Maria Sharapova.
Djokovic's 40-0 start to 2011 is the second-best opening streak in the Open era, which started in 1968.
"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, two-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 of France, who advanced Friday with a 6-2, 6-3, 3-6, 6-3 victory over Thomaz Bellucci.
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.
The seventh-seeded Sharapova moved into the fourth round by overpowering Yung-Jan Chan of Taiwan 6-2, 6-3.
Gilles Simon beat No. 10 Mardy Fish 6-3, 6-4, 6-2. That result, plus Vania King's 6-4, 6-2 loss to No. 9 Petra Kvitova of the Czech Republic, means there are zero U.S. men or women left in the singles draws as the tournament enters Week 2.
Only one other time in the Open era were there no Americans in the round of 16 at a Grand Slam tournament — the 1973 Australian Open, when no one from the United States entered the field.
