Roger Federer, who gives the illusion of making time stop, is enjoying his return to Paris after an absence of four years, as any 37-year-old tennis genius would, and he confirmed on day six he is still dangerous going into the second week for the 14th time in his career.

Federer has looked fit, sharp and happy in his first three matches, has not dropped a set and is hitting the ball with pleasing power and precision, as the young Norwegian Casper Ruud discovered on Court Suzanne Lenglenon Friday when Federer floated past him in a little over two hours, winning 6-3, 6-1, 7-6 (8).

“A few months ago I didn’t know what to expect,” he said later. “Now I know where my level’s at. I still don’t know exactly where my absolute best is but I feel like it could be there. Maybe not. I’m happy to find out, either way.”

Federer has still got plenty of life in those lithe legs, as he showed when he took the first set with an athletic smash after 37 minutes of solid tennis. Thereafter the old boy strolled through to the fourth round in his 400th match at a major.

Although it got a bit tight at the end when Ruud saved three match points in the tie-break before handing Federer a fourth, the Swiss put the winner away as if swatting a fly. It was as if he decided he would finish it as stylishly as he started.

Ruud’s father and coach, Christian, was in the main draw when Federer made his grand slam debut in Paris 20 years ago, although they never met on court. The same goes, as it happens, for his first three unseeded opponents this year, Lorenzo Sonego, Oscar Otte and Ruud, which is unusual, the Swiss admitted, given he has been playing long enough to now have beaten players from 58 different countries.

Rafael Nadal celebrates a hard-earned win over David Goffin. Photograph: Clive Brunskill/Getty Images

Federer was generous to his opponent, as he normally is. “I liked how he figured things out after going on a tough run of nine games [lost]. The third set could have gone either way. It was nice to see him hang in there. He’s very focused, he’s got good energy.”

Then again, it would be surprising if they ever met on court again. Federer, who is 38 in August, may well be playing his last French Open; he refuses to join the speculation, one way or another, saying only he has not set a retirement date.

And while Ruud, who is 20 and ranked 63 in the world, has the majority of his career in front of him, he will probably need to get inside the seedings at majors to avoid the big beasts in early rounds. This was a high point, even though he lost.

Federer added: “I enjoyed the match. I thought it was tough, even though I had a good run there for a while. That also is very important for me to know: that I can run through a set and a half and just take care of business.”

He next plays Leonardo Mayer, who wore down the French marathon man, Nicolas Mahut, 3-6, 7-6 (3), 4-6, 7-6 (3) in what seemed longer than the registered three hours and 27 minutes.

If Federer is on fire, so too is Rafael Nadal, although he stuttered for the first time in this tournament when he dropped a set – only his 26th at Roland Garros in 15 years – on his way to beating David Goffin 6-1, 6-3, 4-6, 6-3 on Court Philippe Chatrier.

Like Federer, he is in the fourth round for the 14th time, both of them eclipsing the long-standing record of Budge Patty. After this tough interlude, his ridiculously easy draw continues on Sunday.

Injury and illness continue to blight the tournament, and Benoît “The Hair” Paire – surely the only athlete in tennis with a sponsored beard – was relieved to have made it into the fourth round at the 10th attempt when Pablo Carreño Busta retired with a right thigh injury after three sets.

Paire, who resembles a tall French Ned Kelly, led the Spaniard 6-3, 4-6, 7-6 (1) after just over two hours of an entertaining match on the new garden court, Simonne-Mathieu. He knows one thing about his next opponent, Kei Nishikori: he will be tired.

The seventh seed spent four hours and 26 minutes in the Bullring beating Laslo Djere 6-4, 6-7 (6), 6-3, 4-6, 8-6. That is the second longest match of the first week – seven minutes behind Paire’s own slog against his compatriot Pierre-Hugues Herbert.

Nishikori later gave the Serb credit for making it such an engrossing contest. “He almost had it. It was nice to come back from 3-0 down, two breaks. It wasn’t easy. He was on fire.”

Fire seemed to be the theme on Friday, with plenty more to come.