Last year, Kerber fell in the first round at Roland Garros, losing to Kiki Bertens of the Netherlands.
Kerber, who ended Serena Williams' stay atop the WTA rankings a year ago, was gone from Roland Garros by lunchtime on Day 1, putting up little resistance while being beaten 6-2, 6-2 by 40th-ranked Ekaterina Makarova of Russian Federation.
Add in that 23-time major champion Serena Williams is pregnant and won't play until next season, and five-time major champion Sharapova was refused a wild card in Paris as she returns from a 15-month doping suspension, and the rest of the field might have more reason than usual to believe in the chance to claim a Grand Slam trophy.
Angelique Kerber could face an embarrassing first-round exit at the French Open if the world number one takes her poor claycourt form into her first round match against Russian Ekaterina Makarova on Sunday.
This marked Kerber's 11th consecutive trip to the French Open with her best coming in 2012 when she reached the quarterfinals.
Makarova nailed three games in a row into the second set, before Kerber broke in the fourth game in an unfamiliar manner.
Makarova will go on to face Ukraine's Lesia Tsurenko in round two. I have to find myself again and try to forget the clay season as soon as possible, and reset for the grass season again.
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The double Wimbledon champion, who required almost four hours of surgery on the tendons and nerves in her left playing hand after being stabbed by an intruder during a burglary at her apartment in the Czech city of Prostejov in December, breezed past American Julia Boserup 6-3, 6-2 in front of her parents and brothers on Court Philippe Chatrier.
Kvitova was playing for the first time since she was stabbed during an attempted burglary at her home in the Czech Republic in December. Williams, who is seeded 10th, saved two set points to win 6-4, 7-6 (3). Gave her a big hug.
In the men's event, sixth seeded Dominic Thiem, the only man to beat Rafael Nadal on clay this year, made quick work of Australia's Bernard Tomic 6-4, 6-0, 6-2. Ruano Pascal won swiftly in 67 minutes, and Hingis revealed afterward that her preparation for Wimbledon was inhibited by tendinitis in her lower back.
That setback came just a year after Ruzici won the French Open.
Olympic champion Monica Puig sent veteran Italian Roberta Vinci to her 10th first round loss in 13 visits, winning 6-3, 3-6, 6-2.
Her staggering longevity is illustrated by the fact that her potential second round opponent is compatriot Amanda Anisimova who, at just 15, is the youngest main draw competitor since 2005.
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