(CNN) -- Australian Open champion Li Na fell at the first hurdle of the French Open Tuesday as she was defeated by the unseeded Kristina Mladenovic of France 7-5, 3-6, 6-1.
The world No. 2's early exit follows that of men's Australian Open champion Stanislas Wawrinka, who lost Monday to Spanish outsider Guillermo Garcia-Lopez.
For Mladenovic, the victory marked just the fifth match she has won this year.
The 21-year-old won the girls title in Paris in 2009 but has struggled to replicate this success in the seniors and is currently ranked 103 in the world.
"After the draw I wasn't very happy, but I made sure I prepared as well as I could and was ready to play my best tennis," Mladenovic said in her post-match interview on Suzanne Lenglen.
"When I got on court, I thought, 'I'm at home, be positive.'
"I tried to get my forehand into play and attack her forehand whenever I could and it worked well. I'm really glad I could produce such good tennis in front of all these supporters."
Li, a French Open winner in 2011, committed 37 unforced errors compared to her opponent's 25 and surrendered meekly in the final set.
Her defeat marks the first time a ladies Australian Open winner has lost in the first round of the French since Lindsey Davenport in the year 2000.
Unsurprisingly, Li cut a dejected figure in her post-match press conference, telling reporters: "Nobody says if you're number two in the world you have to win all the matches. I mean, this is tennis.
"I think it doesn't matter who plays today against me, I always lose because I don't think I put pressure on her. I think today I gave away the match. I think today is not about tennis, so many things are wrong."
Elsewhere on Tuesday, Denmark's Caroline Wozniacki was eliminated 7-6, 6-4, 6-2 in the opening round by Belgium's Yanina Wickmayer.
The 13th seed, whose engagement to golfer Rory McIlroy was broken off last week, has only once advanced past round three in Paris -- in 2010.
Fourth seed Simona Halep, from Romania, cruised past Russian opponent Alisa Kleybanova 6-0, 6-2 in just 55 minutes and will now face Britain's Heather Watson who overcame Barbora Zahlavova Strycova, from the Czech Republic.
Serbian No. 6 seed Jelena Jankovic and compatriot Ana Ivanovic -- the 2008 winner -- both secured second round berths, as did 21-year-old American Sloane Stephens.
In the men's draw, fourth seed David Ferrer, from Spain, made light work of his opening encounter, dispatching Dutchman Igor Sijsling 6-4, 6-3, 6-1.
Andy Murray, the reigning Wimbledon champion, took four sets to see off the challenge of Andrey Golubev from Kazakhstan, 6-1, 6-4, 3-6, 6-3.
Murray has been trying to rediscover his best form after back surgery last year and he told the tournament's official website: "I've been moving fairly well the last couple of weeks.
"It was windy, especially at the start. You want to dictate as many points as you can but when it's breezy, it's tricky to stick to your tactics. I didn't go for my shots too much. I just tried to be patient."
Murray has been without a coach since parting with Ivan Lendl earlier this year, but he joked that he is finding it hard to appoint a successor.
"Have I found a coach? Hopefully soon. I'm trying but not many people want to work with me so it's not that easy," he added.
Gregor Dimitrov, the No. 11 seed from Bulgaria, was dumped out by Croatian veteran Ivan Karlovic, who won his first match at the French Open since 2007.
There were also wins for France's No. 12 seed Richard Gasquet over Bernard Tomic, of Australia, and his compatriot Gael Monfils.