Back hurts but Nadal stays on course in Paris
Spain's Rafael Nadal hits a return to Argentina's Leonardo Mayer during their French Open third round match at the Roland Garros stadium in Paris on May 31, 2014 - by Kenzo Tribouillard
Seeking to become the first man to win five straight titles in Paris and the first to win nine times at the same Grand Slam, Nadal has lost just 19 games in getting to the last 16.
At the same stage last year en route to his eighth French Open title, Nadal had dropped two sets and lost 48 games.
Mayer, ranked 65th in the world, had little to offer as Nadal led from the start and was able to play well within his limits and still race away with the match.
The only blip came in the eighth game of the second set when Mayer broke for the first time in the match to level at 4-4.
But minutes later Nadal snuffed out any nascent threat to go two sets clear and the outcome was a formality after that.
The Spaniard's record at Roland Garros since 2005 is now 62 wins for one loss, that coming against Robin Soderling of Sweden in a 2009 fourth round match.
"It was a positive first week - under control and winning in straight sets is better and I'm happy for that," he said.
Only cloud on the horizon for Nadal was ongoing problems with his troublesome back that caused him to take some of the pace off his serve.
"I felt a little bit my back, that's why I slowed down a little bit the serve," he said.
"I had the problem in Australia. It's real, but during my career I have had a few problems."
Next up for the Spaniard, who will turn 28 on Tuesday, is little-known Serb Dusan Lajovic, who saw off American hope Jack Sock 6-4, 7-5, 6-3.
Asked if he would asking for advice on how to tackle Nadal from fellow Serb Novak Djokovic, Lajovic wryly replied: "Yeah, I will try to ask everybody some tips against Rafa.
"You need to have a lot of tips and confidence to beat him, but I hope to enjoy the match if he wins and to give my best."
The man Nadal defeated in last year's final, fellow Spaniard David Ferrer, also reached the last 16 by defeating Andreas Seppi of Italy 6-2, 7-6 (7/2), 6-3.
The fifth seed had little difficulty in despatching a player he had taken on six times previously and not dropped a single set.
He will now go on to take on 19th seed Kevin Anderson of South Africa who moved through when opponent Ivo Karlovic of Croatia retired with a back injury after losing the first set 6-3.
With 35-year-old Karlovic measuring 2.11m (6ft 11in) and Anderson 2.03m (6ft 8in) their towering showdown out on Court 2 had been billed as the tallest match in Grand Slam history, but it lasted only 43 minutes.
Anderson also reached the last 16 last year in Paris, the first South African to do so since Wayne Ferreira in 1996.
At 32, Ferrer was one of 10 men aged 30 or over to reach the third round, the most at any Grand Slam event since 1978 Wimbledon when there were 12.
- Setback for US hopes -
American hopes of having three players through to the last 16 for the first time since 1995, when Andre Agassi, Michael Chang and Jim Courier reached that stage, were shattered with defeats for Sock and Donald Young who was edged out 6-2, 6-4, 2-6, 6-7 (7/4), 6-4 by Guillermo Garcia-Lopez of Spain.
John Isner made the fourth round on Friday .
French interest was high on Saturday with Gael Monfils and Richard Gasquet both hoping to join Jo-Wilfried Tsonga in the fourth round.
Monfils came through another punishing battle with Italian 14th seed Fabio Fognini, winning 5-7, 6-2, 6-4, 0-6, 6-2 after looking to be on the point of abandoning at one point at the end of the fourth set.
"I'm dying. I'm about to collapse," he told the umpire at a changeover, but he promptly moved 3-0 up and, in front of an adoring home crowd, he eventually gained revenge for a 9-7 fifth set loss to Fognini in a 2010 second round match.
Gasquet though was unable to complete his match against tough Spaniard Fernando Verdasco, their tie being held over until Sunday due to bad light with Verdasco ahead 6-3, 6-2, 2-2.
Also left with unfinished business were British seventh seed Andy Murray and Germany's Philipp Kohlschreiber who were level 7-7 in the fifth set when they were brought off.