PARIS (AFP) - Second seed Ana Ivanovic of Serbia reached the last 16 of the French Open on Friday with a 6-4, 6-1 win over Caroline Wozniacki of Denmark. Ivanovic will play the winner of the all-Czech match opposing Iveta Benesova and Petra Cetkovska for a place in the quarter-finals. French Open drawcards Rafael Nadal and Maria Sharapova survived French Open scares on Friday but 2002 women's champion Serena Williams was knocked out in her worst performance in Paris since 1999. Nadal, bidding to emulate Bjorn Borg as the only man to win four successive Roland Garros titles, needed treatment on his blistered right foot before brushing aside Finland's Jarkko Nieminen 6-1, 6-3, 6-1 to make the last 16. Sharapova, the top women's seed who is seeking a French Open to complete a career Grand Slam, dropped a set for the second match in a row before seeing off colourful American Bethanie Mattek 6-2, 3-6, 6-2 to reach the third round.But Williams's eighth Roland Garros appearance came to a disappointing third round end losing 6-4, 6-4 to Slovenia's Katarina Srebotnik to suffer her earliest Roland Garros exit since playing as a 17-year-old in 1999. World number two Nadal, who has now won all of his 24 matches here, had to play Tuesday and Wednesday to see off Thomaz Bellucci as torrential rain earlier in the week played havoc with the schedule. He was then back on court on Thursday to see off French qualifier Nicolas Devilder.After cruising through the first two sets against fellow left-hander Nieminen, he required a lengthy medical time-out to have his blistered right foot treated and dressed. Despite the injury, Nadal still cruised to victory in under two hours on the back of two breaks of serve in the third set against Nieminen, the man who brought Andre Agassi's Roland Garros career to an end in 2005. He will now face either fellow Spaniard Fernando Verdasco or Russian 15th seed Mikhail Youzhny for a place in the quarter-finals. Sharapova had led her second round match with Mattek by a set, but a break down 2-3, when it was called off for the night on Thursday.The American then levelled before Sharapova overpowered her opponent with her battery of groundstrokes and will now face Italian Karin Knapp for a place in the last 16."It's been a strange tournament so far, from the first round, playing in very difficult conditions to a long wait yesterday," said the world number one."Then today I wake up and you feel like you're playing a different match in a another tournament. It's been kind of strange, but the good thing is I still have a match ahead of me." Williams looked out of sorts from the start quickly falling a service break down as the 27-year-old Srebotnik, who had lost her three previous meetings against the American, cleverly mixed her shot-making. It was a similar story in the second set as Williams, the 2002 champion when she beat sister Venus in the final, hung on grimly only to drop her serve again fatally in the ninth game. Srebotnik let two match points slip by at 40-15, but clinched it on the next one as Williams hit a looping forehand wide. It was the biggest win of Dubai-based Srebotnik's career taking her into the last 16 at Roland Garros for only the second time in 10 attempts. The 27th seed will play the winner of the match between Emilie Loit of France and Patty Schnyder of Switzerland for a place in the quarter-finals. "It helped a lot that I already played her two or three months ago in Charleston. I learned a lot from that match," she said. "I played tactically well. I dug deep and played well on the big points. With the nerves and everything I did really well today." Williams said she was at pains to explain how she had failed to fathom out how to get on top of her opponent. "I just felt like I missed a lot of easy shots and a lot of key points that I felt could have turned the match around. I wasn't able to capitalize on that," she said. Sister Venus, the eighth seed, was scheduled to play the last match on the Philippe Chatrier Centre Court against Italian claycourter Flavia Pennetta who beat her in Bangkok last year the last time they played. Second seed Ana Ivanovic, who lost last year's final to Justine Henin, looked comfortable, after a sluggish start, in despatching rising Danish player Caroline Wozniacki 6-4, 6-1. Ivanovic will face Petra Cetkovska for a place in the quarter-finals.