PARIS -- For one compelling stretch of Saturday's third-round match at Roland Garros, it looked as if Serena Williams had tapped into the queen within, as well as the word featured in the print design of her competition apparel.

Down a set and a break, 3-2, against aggressive and seemingly fearless player-in-waiting Sofia Kenin, Williams looked disconsolate during the changeover. But the 20-year-old Kenin began to show small signs of frustration in her next service game. A visible surge of adrenaline coursed into Williams' game and shone from her eyes in a few imperial glares.

The crowd at Court Philippe-Chatrier -- always game for three sets -- began to back the lioness over the cub. Williams broke Kenin's serve on her fourth try and then held her own until the set was level at 5-all.

Williams came into the 2019 French Open without enough matches in her legs to have enormous expectations in the Grand Slam event she has won three times. Pride, aura and her famous fight dug her out of holes in her first two matches. It wasn't to be this time, as the younger American's powerful groundstrokes and sharp, strategic shot-making were too much to overcome in a 6-2, 7-5 win.

She played "unbelievable," Williams said of the 35th-ranked Kenin. "In that first set in particular, she hit pretty much inches from the line, and I haven't played anyone like that in a long time."

An exhilarated Kenin, talking many miles per minute, told reporters she handled the momentum swing as best she could. "I actually did feel like, 'OK, Serena is getting there, she's on a roll,' and I knew I had to somehow stop it," she said. "I did feel some stares there, but I tried not to overthink it and do what I needed to do and do what I do best."

Maxime Kouyate, who assists Kenin's father, Alex, in coaching Kenin in South Florida, said her tactics were important but secondary to mindset. "Change the pace, do some drop shots, move Serena as much as she could, but the most important part of this was to believe she could win the match," said Kouyate, who also has traveled with Jo-Wilfried Tsonga on the men's tour.

A newer member of tennis royalty was upended earlier in the day. Like Williams, No. 1 Naomi Osaka started unsteadily on the red clay she finds most challenging for her power game but lifted her level in a sensational, second-round win against a resurgent Victoria Azarenka.

Serena Williams' loss against Sofia Kenin was her first during the first week of any major since Wimbledon in 2014, when she lost against Alize Cornet in the third round. AP Photo/Christophe Ena

By the time Osaka got to her next encounter against No. 42 Katerina Siniakova of the Czech Republic, Osaka had wrung herself out with stress -- her consuming desire to perform well at her first major since earning the top ranking, her outsized desire to win a third straight Grand Slam event. She lost 6-4, 6-2 in 77 minutes.

"You know, it's weird, but I think me losing is probably the best thing that could have happened. I think I was overthinking this, like, calendar slam," Osaka said. "For me, this is something that I have wanted to do forever, but I think I have to think about it like, if it was that easy, everyone would have done it."

Williams, a player who has swept the calendar and more on the way to 23 Slam singles titles and has little left to prove or chase, still finds herself hungry in the moment and dissatisfied when she can't rise to it. Habitually quick to her postmatch news conferences after a loss, Williams arrived so hastily that No. 4 Dominic Thiem of Austria was asked to switch to a smaller interview room to accommodate her, prompting a brief kerfuffle.

Serena's 2019 Season Australian Open: Held 5-1 lead in third set and squandered four match points against Karolina Pliskova in quarterfinals; lost 7-5 in the deciding set.

Indian Wells: Retired in second set of third-round match vs Garbine Muguruza (viral illness).

Miami Open: Withdrew before third-round match (knee injury).

Rome: Withdrew ahead of second-round match with sister Venus (knee injury).

French Open: Lost in third round to American Sofia Kenin; 1st time losing in 1st week of a major since 2014 Wimbledon (3rd round).

She was already looking forward. "I'm definitely feeling short on matches, and just getting in the swing of things," Williams said. "I don't really like playing out points when I practice. I have some time on my hands, so maybe I'll jump in and get a wild card on one of these grass-court events and see what happens."

The pair of upsets Saturday prevented a potential high-celebrity-wattage Williams-Osaka match in the quarterfinals. Instead, Kenin will face Australian 8-seed Ashleigh Barty, while Siniakova will take on 2018 French Open semifinalist Madison Keys of the United States in the fourth round. And Kenin, who since age 5 has had her own website dedicated to her tennis career, now has a real seat at the grown-ups' table and the higher level of attention that will come with it.

Alex Kenin and his wife, Svetlana, immigrated to the United States via Austria and Italy in 1987. "Try to go to another country with $286," he said, smiling, of that journey. The couple returned briefly to Moscow to have extended-family support when Sofia was born.

When the family initially lived in New York, Alex worked as a computer programmer and Svetlana as a nurse. They moved to Florida after Sofia showed exceptional hand-eye coordination, and they were encouraged by veteran coaches Rick Macci and Robert Lansdorp. That potential was confirmed when Kenin won the U.S. Tennis Association's girls 18s championship, and she recently has been tested in pressure situations on the American Fed Cup team.

"If I had known what I would have to go through -- thank god I didn't in the beginning," Alex said. "I cannot call it hard. What can be better than spending every day with your daughter and having a common goal?"

While he spoke, Sofia disappeared briefly. Having played the real Serena Williams, she posed for a picture with a poster of the champion, dreaming of the day when she might join her on that wall.