Roger Federer kicked off only his second French Open campaign in six years with an impressive dismissal of Denis Istomin on Monday, while reigning women's champion Iga Swiatek and men's second seed Daniil Medvedev both reached round two. The 39-year-old Federer, level with Rafael Nadal on 20 Grand Slam singles titles, saw off Uzbek Istomin 6-2, 6-4, 6-3.
"It's a great pleasure to return. It was important to have some rehabilitation and lots of training," said Federer, seeded eighth.
Poland's Swiatek, celebrating her 20th birthday, saw off her good friend Kaja 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 his poor clay-court form behind him by beating the dangerous Alexander Bublik 6-3, 6-3, 7-5.
Later on Monday, Serena Williams will play the first night-session match in the competition's history.
The 23-time Grand Slam champion's meeting with Irina-Camelia Begu of Romania will be played behind closed doors, though, due to a 9pm Covid-19 curfew imposed by the French government.
Federer arrived to Roland Garros having played only three matches since his Australian Open semi-final loss to Novak Djokovic last year, before the Covid-19 pandemic hit.
The Swiss great lost to Pablo Andujar in his first clay-court match of the season earlier this month in Geneva, but struck 48 winners as he raced to victory over Istomin.
But he has been keen to play down any thoughts that he can add to his 2009 Roland Garros title.
He is competing in the tournament for only the second time since 2015 and the first time since reaching the 2019 semi-finals.
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 court after the match for her birthday.
"Obviously it's different. It's more stressful a little bit."
Medvedev ends miserable run
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 US 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 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".
Organisers 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, sixth seed Bianca Andreescu was dumped out after losing a marathon first-round match with Slovenia's world number 85 Tamara Zidansek 6-7 (1/7), 7-6 (7/2), 9-7.
Italian teenager Jannik Sinner, the men's 18th seed, saved a match point against home favourite Pierre-Hugues Herbert to win 6-1, 4-6, 6-7 (4/7), 7-5, 6-4.
In-form Norwegian 15th seed Casper Ruud got the better of Benoit Paire 5-7, 6-2, 6-1, 7-6 (7/4), while former women's finalist Marketa Vondrousova came from a set down to beat Kaia Kanepi.