Roger Federer labelled himself an outsider after making a winning return to the French Open.

The 20-time grand slam champion is playing the year's second major tournament for the first time in four years and had no trouble finding his feet on the redeveloped Court Philippe Chatrier as he dispatched Italy's Lorenzo Sonego 6-2 6-4 6-4 in just an hour and 41 minutes.

Federer had skipped the entire clay-court season for the last two years before making his return earlier this month in Madrid.

"It's nice to be an outsider," said Federer. "That's how I feel, anyhow. Just see how it goes. I know when Wimbledon comes around, sure, I'll be probably a higher favourite. That's OK, too. I'm happy that I'm there where I am.

"But for many years it was if I don't win, it's a disappointment, and you explain yourself in the press room. People don't understand why you lost. I feel like if I lost (here) first round or in the finals or wherever it is, people would be, like, 'OK, that could have happened'.

"I like that approach for me also once in a while. It relaxes you on the bigger points maybe, or it relaxes you subconsciously as you walk through the grounds and go to practice and go to the press room.

"This is not a show I'm putting on. This is the truth. I really don't know how far I can go in this event and I am very happy with my first round. It was a really good performance, I thought, from my side for not having played here for as long as I did."

Federer is worshipped as fervently at Roland Garros as anywhere, and the fans showed how thrilled they were to have the 37-year-old back, with a rousing ovation as he strode onto court.

They were not to be disappointed by the tennis either, Federer deploying his full repertoire to move into 4-0 leads in both the first two sets.

Sonego, a 24-year-old Italian ranked 73rd, dug in well from there, retrieving one of the breaks in the second set and then matching his rival in the third until the crucial break at 4-4.

Federer was never under any real pressure, though, and that was just the way the Chatrier crowd wanted it.

"The reception I got today was crazy," he said. "It was really nice to see a full stadium for a first round like this. It was a beauty. So I'm very, very happy.  I feel that the public missed me, and I missed them, as well."

Federer next faces German lucky loser Oscar Otte, who won his first grand slam match against Malek Jaziri.

Sixth seed Stefanos Tsitsipas could be waiting for Federer should he reach the quarter-finals, and the Greek comfortably moved through to the second round with a 6-2 6-2 7-6 (4) victory over Maximilian Marterer.

Elsewhere, last year's semi-finalist, Italian 16th seed Marco Cecchinato, was a
first-round casualty, losing 2-6 6-7 (6) 6-4 6-2 6-4 to veteran Frenchman
Nicolas Mahut.

Cecchinato, who stunned Novak Djokovic in the last eight 12 months ago, had led by two sets to love but 37-year-old wild card Mahut fought back to give the new garden court Simonne Mathieu its first classic match and take his biggest scalp on his 17th appearance in the main draw here.

Kei Nishikori and Marin Cilic both won in straight sets while struggling Grigor Dimitrov let a two-set lead slip against Janko Tipsarevic before eventually prevailing in five.

There was disappointment, meanwhile, for 25th seed Felix Auger-Aliassime, who withdrew from the tournament with a groin injury.

The exciting 18-year-old Canadian is hopeful of being fit for the grass-court season.