The French Open saw its first major shock as defending women's champion Jelena Ostapenko was sent out in the first round by world number 67 Kateryna Kozlova 7-5, 6-3. The Ukranian recorded her first Top 30 win and advanced to the second round of a major for the first time in her career.

The fifth seed was felled by poor serving, committing 13 double faults and sloppy play off of the ground, 48 unforced errors consigning the Latvian to the record books, joining Anastasia Myskina in 2005 as the only reigning Roland Garros champions to exit in the opening stage.

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Kozlova wins seesaw first set

The double fault woes began early for Ostapenko, hitting a pair in the third game to surrender an early break to Kozlova and with it a 2-1 lead. Ahead 3-2, the Ukrainian faced a break point of her own, but erased it with a drop shot that would force an error from the Latvian -- a shot she would smartly employ throughout the match.

It was clear Ostapenko was struggling in every phase of her game, but she did manage to hold and was back level at 4-4, scorching a backhand winner while up at the net. That game started a run of four consecutive breaks of serve, which would end with Kozlova back ahead at 6-5 after smacking a forehand service return winner down the line.

The world number 67 ended the streak of breaks by serving out the set, Ostapenko one set away from making dubious history, more than doubling Kozlova’s unforced errors in the opening frame (29 for the Latvian as compared to 14 for the Ukrainian).

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Ukranian completes upset to reach maiden second round at a major

Kozlova took a medical timeout following the first set to have a blister on her foot treated and Ostapenko, for a rare time in the match, was able to take advantage, jumping out to a 2-0 lead. She was unable to sustain any momentum she built up and the set was back on even terms.

The seventh game proved to be the decider as the Ukranian tried to put the match away, Ostapenko double faulting twice more to give Kozlova a 15-40 lead. The world number five fought those off with a service winner and a backhand winner to get back to deuce, but a forehand error gave Kozlova another break point, and Ostapenko double faulted for a third time in the game,

The finish line was now in sight, Kozlova winning points with aces and volleys at this stage, and she held for 5-3 by forcing another error from the defending champion with a solid backhand. 

Ostapenko served to keep her title defense alive but two more miscues queued brought up double match point for Kozlova. On the second opportunity, one final Ostapenko backhand went awry into the net, the Ukranian sending shock waves through the women's draw.

Kozlova advances to a second-round match against the winner of Monday's match between Katerina Siniakova and Victoria Azarenka.

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Kozlova talks about her win

Following her stunning victory, Kozlova downplayed her expectations coming into the match, saying "I didn't expect anything from the match. I just went to enjoy every moment on the court because, before, I was not sure if I will be able to play in French Open. So I was just happy to be on court, back on court, and compete. So it was very important for me. And, in the end, the result comes up and it's just amazing."

She explained why she wasn't sure of her ability to participate in Paris: "I got injured in Indian Wells and I get hurt in the knee. There was a chance, maybe, that I would have to go for surgery. But luckily I met very good physios and professionals, and I went for rehab to Tenerife, and they did a great job. And after two months, I come back, and I already played last week. So we avoid the surgery. That was the most important thing."

Now owning a career 3-0 record against Ostapenko, the world number 67 knew"that if I will play her game, that's what she wants, and I'm trying to play differently, and probably this is the reason [for the head-to-head]". She was also aware "this match is different, of course. She had so much pressure".

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Ostapenko laments "a terrible day at the office"

Stating the obvious following her loss, the reigning champion said "I think it was terrible day at the office today for me". She assessed that "in general I played maybe like 20 percent of what I can play. Made like 50 unforced errors and so many double faults. Like, couldn't serve today. Everything together just brought me really bad result."

Ostapenko felt "in the beginning it was okay, but then it just got worse, like, I felt that I'm not myself today on the court. I was just trying to manage and fight until the last point". The Latvian also said Kozlova"was playing very defensive, and I was just making so many unforced errors, which I normally don't do."