Rafael Nadal and Novak Djokovic closed in on a French Open clash, with the Spaniard continuing to look very much the man to beat.
Nadal maintained his record of never having lost to a compatriot at Roland Garros with a 6-1 6-2 6-2 victory over 17th seed Roberto Bautista Agut.
Djokovic also faced Spanish opposition and, after being taken to five sets by Diego Schwartzman last time out, had a more comfortable 7-6 (7/5) 6-1 6-3 victory over Albert Ramos-Vinolas.
Not that it was entirely straightforward as Djokovic, now without coach Andre Agassi after his stay in Paris ended as scheduled, twice found himself a break down in the opening set before fighting back.
He said: "I just didn't start off the blocks the way I wanted. He started very solid, not making errors, and just spinning the ball well, getting a lot of balls back.
"There were a lot of breaks and rebreaks in the first set. But it was very close. It could have gone either way and I'm just glad that I managed to win that tie-break, because after that I started playing with more freedom and more confidence."
Nadal had no such problems. The nine-time champion has dropped only 20 games in the tournament so far - one off his 2012 record.
The only thing niggling the Spaniard, who celebrated his 31st birthday on Saturday, was a time violation given by umpire Carlos Ramos that cost him a first serve.
The pair have history, and Nadal said: "If you want to play well, you have to let players breathe a little. We're not machines that cannot think. That's my viewpoint. But of course I fully respect other points of view.
"I'm telling you this with some type of sadness, because I don't want to have any problems. But this umpire is, I think, trying, in a certain way, to look for my faults, my errors."
Nadal next faces another Spaniard, Pablo Carreno Busta, who finally clinched an epic 4-6 7-6 (7/2) 6-7 (6/8) 6-4 8-6 victory over fifth seed Milos Raonic on his seventh match point.
If the much-anticipated semi-final meeting between Nadal and Djokovic is to take place, the defending champion will have get past sixth seed Dominic Thiem.
The 23-year-old Austrian is yet to drop a set and breezed past Horacio Zeballos 6-1 6-3 6-1.
In the third round, eighth seed Kei Nishikori looked in trouble against young Korean Chung Hyeon when rain stopped play on Saturday, but recovered to win in five sets.
Nishikori had been two sets up but Chung fought back and was 3-0 up in the fourth when play was called off.
The 21-year-old went on to win that set to love but Nishikori hit back to triumph 7-5 6-4 6-7 (4/7) 0-6 6-4 and next meets Fernando Verdasco.
He said: "I think the rain helps me a lot, because I was really down in the fourth set and mentally I wasn't ready.
"I knew I had to change something to beat him today, so I think I made some adjustments to make it a little better than yesterday."
Gael Monfils took the all-French clash against Richard Gasquet when the latter retired with a thigh injury in the third set.
Russian Karen Khachanov became the youngest man to reach the fourth round at Roland Garros since Marin Cilic in 2009 by defeating John Isner.
The 21-year-old won the opening set on Saturday and defused Isner's big serve to win 7-6 (7/1) 6-3 6-7 (5/7) 7-6 (7/3).
