Paris - Roger Federer returns to a new look Roland Garros on Sunday after a four-year absence, admitting he'll be an underdog in his attempt to claim a 21st Grand Slam title.
The 37-year-old Swiss star is the headline act on opening day, 10 years after his one triumph in Paris and two decades since his tournament debut.
Federer, who played his last French Open in 2015, preferring to concentrate his powers on Wimbledon, starts against Lorenzo Sonego, the world No 73 from Italy.
Third-seeded Federer insists that it would be a shock even to him should he manage to prevent either Rafael Nadal from sweeping to a 12th title or Novak Djokovic becoming just the second man to hold all four Slams at the same time twice.
"I feel like I'm playing good tennis, but is it enough against the absolute top guys when it really comes to the crunch? I'm not sure if it's in my racquet," said Federer.
Play on a rebuilt Court Philippe Chatrier starts with women's fifth seed Angelique Kerber taking on precocious Russian 18-year-old Anastasia Potapova, ranked at 81st in the world.
Germany's Kerber is looking for a Roland Garros title to complete a career Grand Slam.
However, the 31-year-old has been suffering from an ankle injury and admitted she is not certain how she will survive the rigours of two weeks on clay.
"Two weeks ago I was not even able to walk really good," she said.
Greek sixth seed Stefanos Tsitsipas is also on Chatrier, facing German left-hander Maximilian Marterer, the world 110.
Tsitsipas made the Australian Open semi-finals in January, beating Federer on the way.
The 20-year-old also defeated Nadal in the Madrid semi-finals before falling to the Spaniard at the same stage in Rome last week.
Second seed Karolina Pliskova closes play on Chatrier against Madison Brengle of the United States.
The centrepiece court of Roland Garros has been demolished and 90% rebuilt since 2018 as part of the 350 million refurbishment of the French Open's historic home.
Fans and players will have to wait to until 2020 to see the retractable roof in operation over the court.
However, this year sees the tournament bow of Court Simonne Mathieu, a 5 000-capacity semi-sunken arena enclosed by greenhouses.
Spain's Garbine Muguruza, the 2016 champion, will have the honour of opening proceedings on the new court against America's Taylor Townsend.
Venus Williams, the 38-year-old American, faces Ukraine ninth seed Elina Svitolina on the same court later in the day.
Williams, runner-up to sister Serena in 2002, made her debut in Paris in 1997.
"I've probably got one of the toughest draws I could have got - Venus Williams," Svitolina told the BBC.
"I don't know why I got this punishment!"
Also in action on the first day at Roland Garros are Italian 16th seed Marco Cecchinato who shocked Djokovic in the quarter-finals in 2018.
Japan's Kei Nishikori, seeded seven, faces France's Quentin Halys on the 30th anniversary of his coach Michael Chang winning the title in Paris.
American seventh seed Sloane Stephens, the 2018 runner-up to Simona Halep, begins against Japan's Misaki Doi.