PARIS， May 24 (Xinhua) -- Roland Garros witnessed a duo of seeded players falling out in women' s singles on Tuesday， when China' s Zhang Shuai and Wang Qiang eased their way into the second round.
World No. 3 Angelique Kerber came out as the first falling seed in a 6-2， 3-6， 6-3 loss to Dutch Kiki Bertens， before fifth seed Victoria Azarenka was forced to retire with a right knee injury late in the evening.
Kerber was broken twice in the first set by the 58th-ranked Bertens， who just won her second career title at Nuremberg on Saturday.
"I'm disappointed that I lost now here the first round， but that's sport and that always happens，" said the Australian Open champion crowned earlier this year. "That was for sure not my best tennis I played today."
The German started feeling a pain in the shoulder in the second set and admitted it' s getting worse.
With the shock win， the 24-year-old Bertens， who made the last 16 at Roland Garros two years ago， advance to the French Open second round to face Italian Carnila Giorgi.
Two-times Australian Open winner Azarenka was trailing 4-0 to world No. 118 Karin Knapp in the decider ahead of her retirement due to injury.
The former French Open semifinalist got the early break to take a 2-1 lead， but it was her Italian opponent who took the first set 6-3 with big serving and hard-hitting shots.
In the second set， Azarenka took an early 2-0 lead and forced the third set with a 8-6 win in a tiebreaker， though the Belarusian seemed uncomfortable， calling for a medical timeout at 3-3 to nurse her right knee.
Azarenka battled tears throughout the third set before conceding at 0-4 to give Knapp the win.
It will be Knapp' s first second round play at Roland Garros since 2008 when she played against Latvia' s Anastasija Sevastova.
Earlier on Tuesday， former top-ranked Chinese Zheng Saisai was beaten in straight sets by No. 22 seed Dominika Cibulkova of Slovakia， as both her compatriots went through to the second round.
The Shaan Xi native committed six double faults and 16 unforced errors throughout one hour and 26 minutes match， and won just one out of her four breaking points before losing 6-3， 6-1 to the 25-ranked 27-year-old.
"I just couldn' t pull myself together this morning，" said Zheng， who' s slipped to No. 85 recently after disappointing trips to clay courts in Madrid and Rome.
"To be an opponent like Cibulkova， you'd got to be more than 100 percent form， and I just played not so well this time."
Asian Games champion Wang Qiang， however， needed just 51 minutes to wrap up a 6-0， 6-0 victory over French wildcarder Tessah Andrianjafitrimo.
The 24-year-old world No. 74 from North China' s Tianjin city will next play the 12th-seeded Spaniard Carla Suarez Navarro， who rallied past Czech qualifier Katerina Siriakova 6-2， 4-6， 6-2.
Australian Open quarterfinalist Zhang Shuai also breezed her way into the second round， resuming a suspended match from 5-5 in the first set and coming out as the eventual winner over 31-year-old Galina Voskoboeva of Kazakhstan 7-5， 6-2.
Zhang' s next opponent is the 21st-seeded Australian Samantha Stosur， who will partner up the Tianjin native in the women' s doubles play starting Wednesday.
In the men' s singles play on Tuesday， No. 1 seed Novak Djokovic defeated 95th-ranked Lu Yen-hsun of Chinese Taipei 6-4， 6-1， 6-1 when the Serbian bidding to complete a career Grand Slam in Paris after losing in the final three times over the past four years.
Andy Murray followed to completed his ninth career comeback from two sets down at Court Philippe Chatrier， erasing that big deficit and beating 37-year-old Radek Stepanek 3-6， 3-6， 6-0， 6-3， 7-5.
They finished the match Tuesday after play was suspended because of darkness Monday night with Murray leading 4-2 in the fourth set.
Another six people were seriously wounded in the attack claimed by the Taliban insurgent group.
The nationalities of the foreign nationals remained unknown.
The incident occurred at around 9:00 p.m. Thursday after four persons who hid pistols in their socks pretended that they came to have dinner in the restaurant of the hotel, which is located near the presidential palace Cheap Men's Nike Air Max Plus Just Do It White Shoes , Interior Ministry spokesman Seddiq Seddiqi told reporters near the site around midnight.
The assailants indiscriminately fired at the people who were dining in the five-star hotel, the source said.
Police checked the security camera and found the attackers looked at the age of 20 or even younger.