Reigning French Open women's champion Iga Swiatek kicked of her title defense campaign with a straight-sets victory over Kaja Juvan on Monday, while men's world No. 2 Daniil Medvedev finally reached round two for the first time at Roland Garros.
Poland's Swiatek, celebrating her 20th birthday, saw off her good friend Juvan 6-0, 7-5 on Court Philippe Chatrier.
Medvedev, who had lost in the first round in all of his four previous appearances in the tournament, put poor clay-court form behind him by beating the dangerous Alexander Bublik 6-3, 6-3, 7-5.
Later on Monday, Roger Federer will start only his second French Open campaign in six years against Denis Istomin, before Serena Williams plays the first night-session match in the competition's history.
The 23-time Grand Slam champion's match against Irina-Camelia Begu of Romania will be played behind closed doors, though, due to a 9 p.m. COVID-19 curfew imposed by the French government.
Swiatek, who became the first major singles champion from Poland last October, hit 22 winners in an impressive opening to her bid for a second straight Roland Garros triumph.
"I tried to put it behind me (being defending champion) and kind of use it in a positive way because I just know that I'm feeling good here," said the eighth seed, who was presented with flowers on the court after the match for her birthday.
"Obviously it's different. It's more stressful a little bit."
It is not just in Paris that Medvedev has struggled on clay. The Russian had lost eight of his previous nine matches on the surface dating back to 2019.
But the two-time Grand Slam runner-up was too strong for Kazakh Bublik, setting up a second-round tie against either Australian wildcard Christopher O'Connell or U.S. player Tommy Paul.
"It was a good match and I've been training really well," said the 25-year-old Medvedev, who lost the Australian Open final to Novak Djokovic in February.
"I'd never won at Roland Garros before so I really wanted to win today. To win in three sets was a brilliant match on my part.
"I struggled in recent tournaments on clay, the balls are suiting me this week though and I hope I can go a long way. I think I move well on clay but I sometimes struggle with getting the power."
Medvedev is bidding to take advantage of being in the opposite half of the draw to 13-time champion Rafael Nadal, Djokovic and Federer, while fourth seed Dominic Thiem was knocked out on Sunday.
The early stages of the 2021 tournament have been overshadowed by Naomi Osaka's controversial boycott of press conferences which have seen her threatened with disqualification from the event.
Her coach, Wim Fissette, told German magazine Der Spiegel on Monday that Osaka wants "to use her status to address problems."
Organizers will be relieved that no other players have followed Osaka's lead so far though.
"In my opinion, just having a good relationship in media, it can help you," said Swiatek after her win.
Elsewhere on Monday, Italian teenager Jannik Sinner, the 18th seed, saved a match point against home favorite Pierre-Hugues Herbert to win 6-1, 4-6, 6-7 (4/7), 7-5, 6-4.
John Isner won the battle of the American big-servers with Sam Querrey 7-6 (7/2), 6-3, 6-4, while former women's finalist Marketa Vondrousova came from a set down to beat Kaia Kanepi 4-6, 6-3, 6-0.
