Serena Williams loses early in a Grand Slam for the third time this season

LONDON -- Another Grand Slam, another disappointing exit for No. 1 Serena Williams. No. 25 Alize Cornet of France pulled off the upset of the tournament,

LONDON -- Another Grand Slam, another disappointing exit for No. 1 Serena Williams. No. 25 Alize Cornet of France pulled off the upset of the tournament, beating the five-time Wimbledon champion 1-6, 6-3, 6-4 in the third round. This is the first time since 1999 that Serena has lost before the fourth round of back-to-back Slams, and this is her earliest loss at Wimbledon since 2005. So far this year, Serena has failed to advance past the fourth round of a major; she was ousted by Garbine Muguruza in the second round of the French Open, and fell to Ana Ivanovic in round four of the Australian Open.

Both players were nervous at the start, as Cornet broke Serena to start only to get broken back. But the match, taking place on the roof-less No. 1 Court, was interrupted by rain early -- the players took shelter at deuce at 1-all with Serena serving in the first set. When the players returned, Serena won five straight games to seal the first set with little trouble. 

Then the match turned. Serena lost five straight games to start the second set and Cornet, who defeated Williams earlier this season in straight sets in the Dubai semifinals, gained confidence. She began dictating play and finished the second set with 11 winners and four unforced errors compared to Serena's eight winners and 11 unforced errors.

Serena's struggles at the Grand Slams continue with loss at Wimbledon

After a tight start to the third set, Cornet again raced away, earning a double-break lead at 5-2 before Williams mounted a comeback. The American won two straight games with some of her best hitting of the day and put the pressure back on Cornet to serve out the match. 

As the pro-underdog crowd roared, Cornet stepped to the line and quickly earned a 30-love lead thanks to two poor unforced errors from Williams. Two points later Cornet held when Williams put a short backhand into the net, and the Frenchwoman screamed in delight after scoring her second straight victory over the American No. 1. After she shook hands with a gracious Williams, Cornet returned to salute the crowd and then kneeled down to kiss the grass that had tormented her for so much of her career.

"I just cannot believe it, a few years ago I couldn't play on grass, I was so bad," Cornet said. She said she struggled to move her legs after the rain delay, but once she warmed up her game finally came. "Finally I'm through, I don't know how -- just the heart and the help of the crowd. It's one of the biggest upsets of the tournament - she won so many times here. I can't believe I did it."

Watch Cornet's massive celebration below:

WATCH: @alizecornet celebrates the upset of the tournament, having defeated No.1 seed Serena Williams. #wimbledon http://t.co/1OS6VO8Wvk

— Wimbledon (@Wimbledon) June 28, 2014

Overall it was a nervous and underpowered performance from Williams, who suffered her earliest exit from Wimbledon since 2005. She finished the match with 29 winners and 29 unforced errors compared to Cornet's cleaner line of 28 winners and 18 unforced errors. Perhaps most surprisingly was her lack of an effective serve. She hit just three aces -- as did the underpowered Cornet -- hit seven double-faults, and won just 30 percent of her second serve points.

"The changes I need to make I think are mostly within. Just try to see why I'm making some errors," Serena said after the match. "But, you know, it's difficult. Like I said, if I'm not playing, you know, a great, great match, these girls when they play me, they play as if they're on the ATP Tour, and then they play other girls completely different. It's never easy being in my shoes. But you got to be ready."

Williams' loss opens up the top half of the draw which includes Maria Sharapova and Eugenie Bouchard. Sharapova won her third round match easily, beating American Alison Riske 6-3, 6-0. Bouchard did not drop a set either, beating Andrea Petkovic 6-3, 6-4 to advance to the second week of Wimbledon for the first time in her young career. Bouchard will play Cornet on Monday.