Child's play for Djokovic and Federer

PARIS (Reuters) - It was child's play again for Novak Djokovic on kid's day at the French Open on Wednesday as the dominant Serb booked a third round slot when Romanian Victor Hanescu retired hurt while trailing 6-4 6-1 2-3.

The 24-year-old took his winning streak from the start of the year to 39 but things could be about to get a little more serious for the world number two who faces 2009 U.S. Open champion Juan Martin del Potro next.

Third seed Roger Federer and last year's women's runner-up Samantha Stosur also found it easy on a hot and sunny day at Roland Garros with wins over France's Maxime Teixeira and Romanian Simona Halep respectively.

Del Potro, whose injury problems seem to be behind him, moved menacingly through with a straight sets victory over Slovenia's Blaz Kavcic.

Women's defending champion Francesca Schiavone of Italy looked impressive in brushing aside Russia's Vesna Dolonts 6-1 6-2 while the most dramatic match was saved until last when German Sabine Lisicki left Court One on a stretcher after blowing a match point and crumbling to a 4-6 7-5 7-5 defeat by world number three Vera Zvonareva of Russia.

Dressed in black, a stark contrast to the white linen dresses and shirts dappling the sunlit stands on court Phillipe Chatrier, Djokovic clinically took Hanescu apart.

The day after world number one Rafael Nadal was forced to come back from the brink in his opening match against John Isner, Djokovic breezed to victory after breaking serve in the 10th game to clinch the opening set.

A series of winners put him two sets up with barely an hour on the clock and Hanescu, who reached the Nice Open final this month, threw in the towel midway through the third set after massaging his left leg.

"It's bad luck for him," a relaxed Djokovic, whose total winning run now stands at 41 including last year's Davis Cup final, said at courtside. "But it's important to spend less time on court in the early rounds."

Looking ahead to a third round that, a couple of years ago could have graced a grand slam final, Djokovic said he expected a tough contest against 25th seed Del Potro who tumbled down the rankings with wrist and hip problems.

"It will be a big challenge for both of us. He deserves to be here," added Djokovic, who would replace five-times French Open champion Nadal as world number one if he reaches the final. "He has amazing groundstrokes and a big serve."

While Djokovic and Nadal hog the limelight, Federer showed he is still a huge threat as he sauntered into the third round by thrashing wildcard Teixeira 6-3 6-0 6-2 in a gentle morning workout as panamas hats bloomed on Court Suzanne Lenglen.

DREADED BAGEL

Swiss Federer, who has not won a grand slam title since the 2010 Australian Open, misfired a few forehands in the opening set before he flattened world number 181 Teixeira.

"I'm very happy with these types of matches," 16-times grand slam champion Federer, who faces Serb Janko Tipsarevic, told reporters. "I can practice more and so on, but now I'm really in the tournament."

Teixeira was not the only player to be given a lesson and little-known Romanian Halep will not forget her's from women's eighth seed Stosur in a hurry. Halep looked like having a dreaded 'double bagel' for breakfast but in the end digested a 6-0 6-2 thrashing in 66 one-sided minutes.

World number one Caroline Wozniacki also reached the third round but was given some anxious moments by Canada's Aleksandra Wozniak who trapped her into a moonballing contest and set up three set points in the second set.

Dane Wozniacki, who has yet to claim a grand slam title, survived the test with some powerful forehands and won 6-3 7-6.

Dark horse Julia Goerges of Germany, the 17th seed, had to battle hard for her 2-6 7-5 6-2 victory over Czech Lucie Safarova but did not let the win go to her head.

Asked who she would pick as the tournament favourite, she quipped: "For sure not me."

Compatriot Lisicki, 21, later seemed set to create the biggest shock so far when she led Zvonareva 5-2 in the third set before imploding. She had her blood pressure checked by the trainer at 5-4, ate a couple of bananas and energizing food, but the world number 121 was still groggy as she bowed out before being carried out of the arena on a stretcher, sobbing.

Other outsiders flew under the radar -- and quite fast.

Spain's David Ferrer, seeded seventh, marched into round three by crushing Frenchman Julien Benneteau 6-3 6-4 6-2 while local favourites Gael Monfils, Jo-Wilfried Tsonga and Richard Gasquet all moved through in some style.

(Editing by Pritha Sarkar and Martyn Herman)