PARIS - What was shaping up as a struggle for Novak Djokovic at the French Open suddenly turned into something of a stroll.

Tied at a set apiece with big-hitting 2009 U.S. Open champion Juan Martin del Potro when play was suspended because of darkness a night earlier, Djokovic quickly faced two break points Saturday.

He saved those, then broke del Potro in the next game, and that was pretty much that.

"If he serves well, he can beat anybody, really," Djokovic said. "I went [into] the match a bit more nervous than usual."

If that's so, it didn't really show. Djokovic completed a 6-3, 3-6, 6-3, 6-2 victory in the third round, pushing his 2011 record to 40-0 and stretching his winning streak to 42 matches overall, including two Davis Cup matches in December.

Djokovic's 42-match run is tied for the third-longest by a man in the Open era, which began in 1968; Guillermo Vilas won 46 in a row in 1977. And Djokovic is off to the second-best start to a season, trailing only John McEnroe's 42-0 in 1984.

No. 4 Andy Murray got past Michael Berrer of Germany, 6-2, 6-3, 6-2, despite badly twisting his right ankle while chasing a drop shot in the second set, then said he wasn't sure if he could play his next match.

France's 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, mean there are zero U.S. men or women left in the singles draws as the tournament enters Week 2.

Twenty-eight of the 32 players still around in both fields are from Europe. That includes three Russian women who won Saturday: No. 7 Maria Sharapova, No. 25 Maria Kirilenko and unseeded Ekaterina Makarova.