Nadal, Murray, Djokovic through

Novak Djokovic, Andy Murray and Rafael Nadal secured safe passages to the third round of the French Open on the fifth day of play.

Number one seed brushed off injury problems in the second set, beating Giles Muller of Luxembourg, 6-1, 6-4, 6-4 in the second round. Throughout the match, the Serb was fidgeting with his right-leg after appearing in some discomfort, which led to a medical timeout in the second set.

"I slipped a lot and felt pain in the right leg," Djokovic admitted post-match. "But I'm not worried about it."

Djokovic increased his winning stretch to 24 games and will lock horns with Australian teenager Thanasi Kokkinakis whose performances have created shockwaves at the tournament.

Meanwhile, Murray, the Australian Open runner-up, won 6-2, 4-6, 6-4, 6-1 over Joao Sousa of Portugal to book a third round tie with another of the exciting Aussie talents on the circuit, Nick Kyrgios.

The Scot's impressive run of form on clay this season under new coach Amelie Mauresmo continues, but he showed signs of mental fortitude when Sousa recovered to win the second set. Murray was given a warning for time violation and admitted he feels he was playing 'too slowly' in the game.

"There were points today where I got told I was playing too slow and I tried to speed up," he said. And I did. But that one point obviously the second time it happened, I was up at the line in good time, and I didn't serve because they were still playing the highlight from the point before."

Defending champion and sixth seed Rafael Nadal enjoyed a 6-4, 6-3, 6-1 victory over Spanish compatriot Nicolas Almagro to set up a third round match against Andrey Kuznetsov. Djokovic and the Spaniard, who is seeking a 10th title, could be set for a quarterfinal showdown at the start of next week, should last summer's French Open finalists win their fourth round matches.

In the men's side on Thursday, five seeded players were eliminated from the tournament, including 31-year-old German and No.22 seed Philipp Kohlschreiber.

Doubts for Williams?

Serena Williams showed some vulnerability against German Anna-Lena Friedsam, but also produced some killer forehand shots to win 5-7, 6-3, 6-3.

With her 20th Grand Slam championship on the line, the American remains as determined as ever to improve her game and avoid another early exit at Roland Garros. "I know I'm capable of playing great tennis, just haven't seen it yet," she said.

"My level is literally a hundred times better than I played today," Williams added. "I think I take more solace in the fact I can play better as opposed to the fact that that's the best I could play. Then I would be in trouble."

In the third round, Williams faces 2013 French Open semifinalist Victoria Azarenka of Belarus who has won both her matches so far in straight sets. But there was defeat for fifth-seed Caroline Wozniacki who was dumped out after losing to Julia Goerges of Germany 6-4, 7-6 (4)

Elsewhere, Wimbledon champion Petra Kvitova, Andrea Petkovic, American Sloane Stephens and Kristina Mladenovic progressed.