PARIS — Roger Federer's return to French Open clay is going so smoothly he still has not dropped a set in reaching the quarterfinals.

The 20-time Grand Slam winner eased through with a 6-2, 6-3, 6-3 win Sunday against unseeded Argentine Leonardo Mayer.

With temperatures reaching 88 Fahrenheit (31 Celsius) on a sun-soaked centre court, the third-seeded Federer did not face a break point in beating Mayer for the fourth time in four meetings.

Federer won his only French Open in 2009 and remains on course for a semifinal showdown with Rafael Nadal, the defending champion at Roland Garros.

The 37-year-old Federer is now into a record-extending 54th Grand Slam quarterfinal overall. He also became the third oldest man to reach the last eight at Roland Garros.

"Of course the hope was to go deep and I'm in the quarters now, so I'm very, very happy at this point," Federer said. "I served super well and Leonardo had trouble returning. I was able to put pressure on him and I'm very happy with my performance."

Nadal was facing another unseeded Argentine, Juan Ignacio Londero, later on Sunday.

After dropping his serve to lose the second set, Mayer angrily swiped the ball away and was given a code violation warning for ball abuse.

Federer was looking so clinical and assured that the crowd at Philippe Chatrier groaned in disbelief when he missed an easy-looking forehand volley at the net, early in the third set.

It was the second time Federer has beaten Mayer at a Grand Slam — the other also coming in straight sets, in the first round of the U.S. Open in 2015. That was also the last year Federer played at Roland Garros, before skipping clay entirely until returning to the surface this year.

Four years ago, Federer lost in the quarterfinals to Swiss countryman Stan Wawrinka in straight sets.

He next faces either Wawrinka or rising star Stefanos Tsitsipas, who beat Federer in the fourth round at this year's Australian Open.

They were playing their fourth-round match Sunday on neighbouring Court Suzanne Lenglen.

Earlier Sunday, Petra Martic followed up her win over second-seeded Karolina Pliskova by rallying past Kaia Kanepi 5-7, 6-2, 6-4 on centre court to reach her first Grand Slam quarterfinal.

The 31st-seeded Croat next faces Czech teenager Marketa Vondrousova, who reached her first quarterfinal at a major without dropping a set. The 19-year-old Vondrousova beat 12th-seeded Anastasija Sevastova of Latvia 6-2, 6-0 in just 59 minutes.

Also advancing to the last eight was 26th-seeded Briton Johanna Konta, who beat 23rd-seeded Donna Vekic 6-2, 6-4. Konta's quarterfinal opponent will be either 2016 champion Garbiñe Muguruza or 2017 U.S. Open champion Sloane Stephens. Their match was following Nadal's on centre court.

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