Paris, May 27 : Australia's Kimberly Birrell produced the biggest shock of the opening week at the French Open, rallying from a set down to knock out fifth seed Jessica Pegula in a dramatic first-round clash.

The World No. 83 came from behind to win 1-6, 6-3, 6-3, marking the biggest victory of her career and causing Pegula's earliest Grand Slam exit in five years. It was also Birrellâ??s first win at Roland Garros and her debut main-draw victory at a major outside her home Slam in Melbourne.

Pegula looked firmly in control early, racing through the opening set in under 30 minutes and stretching her lead to a set and a break after winning eight of the first 10 games. But Birrell gradually settled into the contest, raising her intensity from the baseline and capitalising on crucial moments despite winning fewer total points in the match than the American.

The Australian eventually completed the comeback in one hour and 41 minutes, closing out the upset with fearless shot-making against a player who had consistently gone deep in Paris in recent years.

A visibly emotional Birrell struggled to process the scale of the victory moments after leaving the court.

"I donâ??t really know what to say or think," she said after securing not just her first win in Paris, but her first at a Grand Slam that isn't the Australian Open. "When I saw the draw and saw I was playing Jessie, I knew it would be really tough. I really admire her as a player and person. I tried to take it one point at a time. I thought she played so well in the first set. My goal was to just win one game and slowly gain some confidence.

"So happy I was able to play probably the best match Iâ??ve played on clay, and able to play during a Grand Slam, especially here, itâ??s really really special."

Birrell will next face Oleksandra Oliynykova for a place in the third round.

While Pegulaâ??s campaign ended in disappointment, fellow American Madison Keys enjoyed a far smoother passage into the second round. The 19th seed overcame Belgian debutant Hanne Vandewinkel 6-3, 6-0, recovering from a shaky opening phase to dominate the remainder of the contest.

Keys, a former Roland Garros semifinalist, saved three break points early in the first set before storming through 10 of the final 11 games. She will now take on Croatiaâ??s Antonia Ruzic.

Elsewhere, rising Canadian star Victoria Mboko made an emphatic start to her Paris campaign, defeating Czech youngster Nikola Bartunkova 6-1, 6-2 in just 69 minutes.

Mboko weathered an energetic opening from her opponent before taking complete control from the baseline to secure her spot in round two, where she will meet experienced Czech player Katerina Siniakova.

/IANS