Roger Federer is enjoying the "whole rhythm thing" of playing at a grand slam again but admits he has no idea what he is capable of achieving at the French Open.

The Swiss looked sharp in his first-round match on Monday against Uzbekistan's Denis Istomin, posting a 6-2 6-4 6-3 win – coming through his first match at a major since the 2020 Australian Open and subsequent knee surgery.

It was partly his prowess but perhaps also the shortcomings of Istomin's performance that allowed 2009 champion Federer to put on a show on Court Philippe Chatrier, setting up a clash with a familiar foe in Marin Cilic next.

Federer and Cilic will be going head to head for an 11th time – Federer leads the series 9-1 – and for the first time since the 2018 Australian Open final, which went the way of Basle's 20-time grand slam winner in five sets.

It will be their sixth clash in a slam and at the earliest stage they have encountered each other at a major, with those past tussles also including the 2017 Wimbledon final, when an injury-hampered Cilic lost in straight sets.

Federer spoke after beating Istomin of how it is difficult to gauge what he might go on to manage at Roland Garros.

"In a way, I like this situation, that I don't know what's next, how my next match will be. I don't even know who I play, to be honest," Federer said.

"I take it round by round, match by match. I think it's going to help me, with the way I go about it. I'm very happy I won today. It gives me a chance again to test myself on Thursday, I believe. I don't know when I'm playing.

"So see how I feel tomorrow morning. Just all these things going through practice, coming to the site, seeing people, just this whole rhythm thing.

"It's nice to be back in it."

Federer is in Paris without his family due to COVID-19 restrictions and worries it will be the same story at Wimbledon.

But he added: "We signed up for it. I didn't do rehab to then sit at home again. There's a lot to look forward to."

MEDVEDEV WINS AT LAST

Daniil Medvedev's status as the second seed in Paris was the factor that made it possible for Novak Djokovic and Rafael Nadal to be drawn in the same half of the draw, which is what transpired.

There is an element of farce about Medvedev being seeded above 13-time Roland Garros champion Nadal, because the Russian has gone out in the first round in each of his previous visits to the clay-court slam.

However, on Monday, the world number two made a breakthrough, winning well in a match where he was expected to run into trouble as he earned a 6-3 6-3 7-5 victory over Kazakhstan's Alexander Bublik.

"It doesn't feel different than the Australian Open for me coming into this tournament. Now when I'm coming to these big tournaments feeling like this, I know I'm capable of doing big things," Medvedev said.

"If I lose here in Roland Garros it's probably going to be because my opponent will play really good."

NEXTGEN MAKE EARLY IMPACT

David Goffin, the Belgian 13th seed, lost 6-0 7-5 7-6 (7-3) to 19-year-old Italian Lorenzo Musetti, and it was a day when the sight of 39-year-old Federer turning on the style was balanced by the inspiring sight of the next generation showing their potential.

Musetti's fellow Italian Jannik Sinner is also 19 and is the 18th seed, showing on Monday he has the fight to come through tough battles, rallying from two sets to one down to beat experienced French player Pierre-Hugues Herbert 6-1 4-6 6-7 (4-7) 7-5 6-4.

It was the first time Sinner had won a deciding set in a best-of-five match.

Sinner, Musetti and Spain's Carlos Alcaraz could all be major factors at Roland Garros in future years.

Alcaraz, who turned 18 in early May, followed up his run through qualifying and to the second round of the Australian Open by doing the same in the French capital.

He dropped only 11 games in winning three best-of-three-set qualifiers last week and was too strong for his 24-year-old compatriot Bernabe Zapata Miralles, snatching a 6-3 2-6 6-1 7-6 (7-4) win for a first senior win at Roland Garros.

"I think the mental game is really, really important in this kind of matches," Alcaraz said. "You have to be focused and calm all the match, like three hours and 10 minutes.

"It's really important and not easy to do. In the match I trusted a lot in my physical side. I could play really, really good game during the whole match."