World number three Novak Djokovic booked his place in the quarter-finals of the French Open with a convincing 6-4, 6-3, 6-4 win over local favourite Paul-Henri Mathieu on Sunday.

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The Australian Open champion from Serbia held his nerve in the key moments of the match to set up a meeting with Latvian hopeful Ernests Gulbis.

Djokovic took advantage of Mathieu's sluggish first serve to convert all his four break points and win the first two sets.

Mathieu put up more of a fight in the third but sealed victory on his first match point when the Frenchman netted an easy forehand after two hours and 20 minutes.

Ivanovic, Jankovic in last eight

Serbia's Ana Ivanovic and Jelena Jankovic enjoyed starkly contrasting fourth-round wins at the French Open on Sunday while teenager Ernests Gulbis thrust Latvia on the tennis map.

Second seed Ivanovic played with the urgency of a woman late for a lunch appointment as she ruthlessly dismantled Czech Petra Cetkovska 6-0, 6-0 in 54 minutes on Court Philippe Chatrier.

While Ivanovic's win was painfully easy, Jankovic's was just downright painful.

Jankovic needed a 10-minute medical time-out after game three of the second set against Poland's Agnieszka Radwanska before she crawled past the finishing line with a 6-3, 7-6 victory.

"The whole arm is a mess," said Jankovic, who resembled a wrestler pinned to the floor as the tournament trainer massaged her arm and shoulder back to life.

"I started to feel the pain in the beginning of the second set and since then it's been pain, pain, pain," said the 23-year-old, who will next face Spain's Carla Suarez Navarro.

The Paris crowd had barely got through the scrum at the turnstiles as Ivanovic, who by each passing minute looks like improving on her runner-up finish of last year, showed no mercy against the lamentable Cetkovska.

The unseeded Czech, who had not dropped a set in the tournament, looked like a decent threat going on a high-quality opening rally, but once Ivanovic got her eye in she folded quicker than a bad poker hand.

Ivanovic pounded her with winners and even when the Czech carved out two break points in game five of the second, she slouched with a knowing smile when Ivanovic snuffed out any whiff of a comeback.

"It was much tougher than it probably looked, or the results indicates," said a generous Ivanovic, who has lost a paltry 15 games at Roland Garros so far this year.

"I had to work really hard, and I played almost without mistake today."

Latvia has one man in the world's top 350, and only two women in the top 500, but fortunately for the Baltic state Gulbis is singlehandedly cranking up his country's tennis pedigree.

The world number 80 had already disposed of seventh seed James Blake in round two, and a 6-4, 7-6, 6-3 win over Frenchman Michael Llodra on Sunday earned him his first place in a grand slam quarter-final.

Gulbis, 19, silenced the fiercely partisan crowd on Suzanne Lenglen Court with a barrage of aces and even the unseeded Frenchman's swashbuckling net play could not deny him.

He now awaits the winner of Sunday's fourth-round clash between third seed Novak Djokovic and France's [Images] Paul-Henri Mathieu, the 18th seed.

Three-times champion Rafael Nadal [Images] will later look to take his Roland Garros record to a jaw-dropping 25-0 when he faces fellow Spaniard Fernando Verdasco, the fourth consecutive left-hander the champion will have faced.

Schnyder ends Srebotnik's run

Swiss 10th seed Patty Schnyder ended Katarina Srebotnik's unexpected run to the fourth round of the French Open with a 6-2, 6-4 win on Sunday.

The Slovenian had knocked out Serena Williams [Images], the only former champion in the women's draw, in the third round but was unable to reproduce the heroics on Sunday and went down tamely.

The win put Schnyder through to the quarter-finals here for only the second time, a decade after her last appearance in the last eight.

Schnyder is likely to face much stiffer opposition in the next round as she will face last year's runner-up Ana Ivanovic, who handed unfortunate Czech Petra Cetkovska the dreaded 6-0, 6-0 double bagel on Sunday.

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