During an error-filled first set, Williams was constantly shaking her head and yelling at herself. But the 23-time Grand Slam champion quickly changed the momentum by winning the opening three games of the second set.
After committing 14 unforced errors in the first set, Williams had a total of 10 in the second and third sets. Afterward, Williams seemed more relieved than pleased at avoiding what would have been only the second loss of her career in the first round of a Grand Slam tournament — after her defeat to Virginie Razzano at Roland Garros in 2012.
Top-ranked Novak Djokovic was in control from the start, beating 44th-ranked Hubert Hurkacz of Poland 6-4, 6-2, 6-2.
It's the 22nd consecutive victory in Grand Slam tournaments for Djokovic, who is attempting to become only the second man in history to hold all four major titles at the same time on two separate occasions.
Rod Laver was the only player to achieve the feat when he won all four Grand Slams in 1962 and 1969.
Djokovic also won four straight majors in 2015-16.
Rafael Nadal has made light work of qualifier Yannick Hanfmann, winning 6-2, 6-1, 6-3 to advance to the second round.
The 11-time champion at Roland Garros saved four break points in his first service game on Court Philippe Chatrier but was never troubled again by the 184th-ranked German, who was playing for the first time in the French Open main draw.
Nadal later praised the refurbished showcase court where he won his 11 French titles, calling it "very beautiful."
After throwing up twice on the court, Frances Tiafoe says he was "very depleted" for the fifth set of a 6-2, 4-6, 6-3, 3-6, 6-0 first-round loss to Filip Krajinovic of Serbia.
Tiafoe, at No. 32 the only American seeded in the men's draw, was coming off his best Grand Slam showing, a quarterfinal run at the Australian Open.
He said he didn't think he had food poisoning because he felt fine before the match: "Throwing up during the match isn't something that normally happens to me ... I threw up again when I went to the locker room after the third set. The fifth-set result obviously came to that because (I) was obviously very depleted and had nothing really in me. It was tough to end like that."
In another instance of an American losing to a Serbian in five sets, Denis Kudla was beaten 6-0, 6-7 (7), 5-7, 6-3, 6-4 by Miomir Kecmanovic.
Also, 12th-seeded Daniil Medvedev wasted a two-set lead in a 4-6, 4-6, 6-3, 6-2, 7-5 loss to Pierre-Hugues Herbert of France.
Former No. 1 Caroline Wozniacki wasted a perfect start when she lost 0-6, 6-3, 6-3 to 68th-ranked Veronika Kudermetova in the opening match of the day on Court Philippe Chatrier.
Wozniacki's record this year dropped to 9-8 after her fourth straight loss — including first-round defeats in Madrid and Rome — since reaching the final of a clay-court event in Charleston, South Carolina, last month.
The 13th-ranked Wozniacki announced in October that she has rheumatoid arthritis.
The match marked Kudermetova's debut in the main draw at Roland Garros and the biggest win of her career in terms of ranking. The Russian player hit a whopping 40 winners to Wozniacki's 15.
Two-time Wimbledon champion Petra Kvitova has pulled out of the French Open ahead of her first-round match because of an injured left forearm.
The No. 6-seeded Kvitova tweeted Monday that she has been dealing with pain for a few weeks.
An MRI on Sunday night confirmed a Grade 2 tear, which she said "could get a lot worse" if she played.
She had been due to face Sorana Cirstea on Court Suzanne Lenglen.
Kvitova was replaced in the draw by Kaja Juvan, an 18-year-old from Slovenia who lost in qualifying and will be making her Grand Slam debut.
Play has started at Roland Garros on Day 2 of the clay-court Grand Slam tournament.
Rafael Nadal, Novak Djokovic and Serena Williams — owners of a combined 55 Grand Slam singles titles — are all in action on Day 2 at the French Open.
Each is embarking on a bid to achieve a milestone over the next two weeks at Roland Garros.
Nadal begins Monday against Yannick Hanfmann, a German qualifier who played tennis at Southern California and whose career Grand Slam record is 0-1. Nadal seeks his record-extending 12th championship in Paris, the most for any man or woman at any major tournament.
Djokovic, whose first-round opponent is Hubert Hurkacz of Poland, eyes a fourth consecutive Grand Slam trophy, something only one man has managed in the past 45 years: Djokovic himself.
And Williams, who starts against Vitalia Diatchenko, renews her quest for a 24th major title, which would tie Margaret Court for the most in history.
Other past Grand Slam champs in action on a busy day include Stan Wawrinka and Caroline Wozniacki.
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