Jelena Ostapenko became only the sixth female Grand Slam champion to fall at the first hurdle of her title defence when she lost to Kateryna Kozlova at the French Open
Defending champion Jelena Ostapenko crashed out in the first round of the French Open on Sunday after a 7-5 6-3 thrashing by Ukrainian Kateryna Kozlova.
Defeat meant Ostapenko became only the sixth female major winner to fall at the first hurdle of her title defence, joining Anastasia Myskina, Steffi Graf, Jennifer Capriati, Svetlana Kuznetsova and Angelique Kerber.
"It was terrible day," world number five Ostapenko said.
"I just woke up here and my mood was not amazing. A few things go wrong and you are pissed off, but you try to stay positive. Then you lose a match, and it is no longer possible to be positive."
Former finalist Venus Williams joined the 20-year-old in exiting Roland Garros as the American slumped out 6-4 7-5 to China's Wang Qiang.
Second seed Alexander Zverev had no trouble negotiating his first-round opponent, as he comfortably swatted aside Ricardas Berankis 6-1 6-1 6-2.
Grigor Dimitrov, another player tipped to go deep in the event, powered past lucky loser Mohamed Safwat 6-1 6-4 7-6(1).
Dimitrov's original opponent Viktor Troicki withdrew with lower back pain.
Australia's Nick Kyrgios also pulled out ahead of Monday's contest with compatriot Bernard Tomic with an elbow injury.
World number one Rafa Nadal begins his title defence on Monday with a clash against Italy's Simone Bolelli on Court Philippe-Chatrier.
Belgium's David Goffin appeared to be on his way out of the tournament after losing the opening two sets to Dutchman Robin Haase, but the eighth seed regained composure to win the match 4-6 4-6 6-4 6-1 6-0.
Briton Johanna Konta's campaign ended in disappointment yet again as the 22nd seed was beaten 6-4 6-3 by Kazakhstan's Yulia Putintseva. Konta has yet to win a first-round match at Roland Garros in four attempts.
Venus Williams crashed to a straight-sets defeat in the opening round, losing 6-4 7-5 to China's Qiang Wang on Court Suzanne-Lenglen.
Japan's Kei Nishikori, playing in his first grand slam since last year's Wimbledon, showed no signs of a wrist injury that has plagued him in the past few months as he eased past Frenchman Maxime Janvier 7-6(0) 6-4 6-3.
Lucky loser Mohamed Safwat may have been a last-minute replacement to face Grigor Dimitrov on Sunday but the Egyptian is no stranger to the world number five.
"It's nice to play someone you know for such a long time," Bulgarian Dimitrov said.
"I'm happy when I see players that I've shared courts, practice, matches from juniors. Now we're out here battling on such a court. I think it's great. So you never forget that."
U.S. Open champion Sloane Stephens cruised past Dutchwoman Arantxa Rus 6-2 6-0. The American relentlessly attacked her opponent from the baseline and needed just 49 minutes to wrap up the victory.
France's Gael Monfils started shakily against compatriot Elliot Benchetrit but found his rhythm as the match wore on to comfortably quell the 19-year-old's challenge. Monfils prevailed 3-6 6-1 6-2 6-1.
Australia's Nick Kyrgios withdrew from the tournament with an elbow injury. "Unfortunately I have to withdraw from this year's French Open," the world number 23 said.
"Having consulted with my team and medical experts it is deemed too risky for me to step out and potentially play five sets on clay especially as I have not played a singles match in nearly two months."
Fourth seed Grigor Dimitrov got his Roland Garros campaign off to a good start, powering past lucky loser Mohamed Safwat 6-1 6-4 7-6(1) in the opening match on Court Philippe-Chatrier.
Safwat became the first Egyptian player to contest a grand slam main draw since 1996 after Bulgarian Dimitrov's original opponent Viktor Troicki pulled out with lower back pain.
Bosnian Damir Dzumhur swatted aside American Denis Kudla, winning 6-4 6-2 6-2 to storm into the second round.
Elina Svitolina began her quest for a maiden grand slam with a battling first-round victory over Australia's Ajla Tomljanovic on Court Suzanne-Lenglen. The fourth-seeded Ukrainian prevailed 7-5 6-3.