It gets worse for Serena Williams because she's in the eye of a storm on Suzanne Lenglen. The defending champion, shoulders slumped, has twice been broken by Garbine Muguruza in the second set and is now trailing 3-0.

Image source, AFP

Novak Djokovic is having an easier time on Philippe Chatrier, securing the first set 6-1 against Jeremy Chardy. There are other matches to update you on, of course, with eighth seed Angelique Kerber winning the first set 6-2 against Varvara Lepchenko.

Garbine Muguruza is playing against her childhood hero and is proving to be a handful for the defending champion. The 20-year-old is 2-0 up against Serena Williams in the second set and could be about to launch a tremor through the women's draw.

Piers Newbery
BBC Sport at Roland Garros

"We've already had a few surprises but the shock of all shocks is brewing on Lenglen, where Spain's Garbine Muguruza has taken the first set 6-2 against a very flat Serena Williams. The 20-year-old, ranked 35, is one of the new crop of women considered potential Slam winners of the future, but no-one would have predicted this match as a stepping stone."

Image source, Getty Images

It might be time to start doing our homework on Garbine Muguruza, a 20-year-old from Barcelona who is ranked number 35 in the world. The Spaniard has never beaten a top five player. What an occasion to break the duck.

Serena, of course, not down and out yet - although she is already a break down in the second set. Yikes, cripes, blimey etc.

Yikes. Serena Williams is in a spot of bother against daredevil Garbine Muguruza. The Spaniard has just launched an ace down the 'T' to move to within one point of the first set. And, oh my word, Williams returns long on the next point, allowing the Spaniard to win the first set 6-2.

It's fluffy yellow balls rather than metallic ones which are occupying Novak Djokovic's thoughts at the moment, with the Serb leading 2-1 in the first set against Jeremy Chardy. The first set is currently with serve and both players are looking comfortable.

The bookies would heavily favour Djokovic to come out on top in this contest because France's Chardy has not beaten the second seed in eight previous attempts. Ninth time lucky for the Frenchman perhaps?

Lesson number one has been that seeds often fail to prosper on clay, but we've also learned that Novak Djokovic, who is already trying to master French and probably bakes baguettes in his spare time, also enjoys a game of petanque. "After tennis practice today, played some petanque with kind French gentleman that let me play with them," he tweeted. , external

Image source, Getty Images

There were upsets in both the men's and women's draw on Tuesday, of course, as former champion Li Na and 11th seed Grigor Dimitrov lost on Tuesday. But at least Andy Murray survived a scare in his first-round match against Andrey Golubev, moving into the second round with a 6-1 6-4 3-6 6-3 victory.

Speaking of Serena Williams, the defending champion has started her second-round match against Spain's Garbine Muguruza and the underdog has just broken the top seed for a 2-1 lead in the first set. Surely Serena won't follow in the footsteps of Li Na and Stan Wawrinka?

"This is the biggest win of my life," says Schmiedlova, her voice trembling and hands shaking. "It was unbelievable. I still cannot believe that I won."

The 19-year-old from Slovakia could meet Serena Williams in the third round and said, rather nervously: "I want to beat the other sister."

Image source, Getty Images

Another seed is thrown into the boulevard of broken dreams. Teenager Anna Schmiedlova has come back from a set and a break down to beat seven-time Grand Slam champion Venus Williams 2-6 6-3 6-4.

In the first set, the 29th seed played as if she were a teenager again but her opponent fought back in the second set and overcame some jitters in the decider to beat the American. Venus's mum, though, sitting in the players' box, did not catch much of the action as she was catching up with some forty winks. A case of jet lag if ever there was one.

A number of big hitters will be sliding and slipping on the clay today and this is how the day is will unfold on Chatrier:

Jeremy Chardy (Fra) v Novak Djokovic (Srb) [2]

Jo-Wilfried Tsonga (Fra) [13] v Jurgen Melzer (Aut)

Tsvetana Pironkova (Bul) v Maria Sharapova (Rus) [7]

Selected others:

Serena Williams (USA) [1] v Garbine Muguruza (Esp)

Diego Sebastian Schwartzman (Arg) v Roger Federer (Sui) [4]

Hello! It's the fourth day of the French Open and, if you didn't know already, we will be live text commentating all afternoon on the tennis smorgasbord which is available to us. Some players are toiling on the dirt, others are trying to roll back the years, while one or two are attempting to cause further ripples in the men's and women's draw. It's quite exciting.

Sinister dark sci-fi clouds continue to loom over the French capital, bringing with them wind and gloom, but that doesn't mean the tennis is grim so let's lose ourselves in live sport.