Serena Williams and Naomi Osaka both suffered shock defeats in the third round of the French Open on Saturday.
Williams suffered her earliest grand slam defeat for five years with a third-round loss against fellow American Sofia Kenin.
Not since a defeat in the same round against Alize Cornet at Wimbledon in 2014 has Williams been beaten before the quarter-finals at one of the sport's biggest events.
Twenty-year-old Kenin may be a new name to many fans but she has had a very good year so far and refused to be overwhelmed by Williams' presence in a 6-2 7-5 victory.
Kenin struggled to hold back tears as she said: "It's a lot of emotions. Serena's such a great player and a true champion, so all respect to her.
"Playing against Serena you've really got to fight for every point. She's such a tough player. I'm just so happy with this win."
Williams gave credit to Kenin, saying: "I think she played really well. I feel like she, 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."
The 23-time grand slam champion admitted she is "pretty far away" from being in top shape but believes she does have enough time to correct that for Wimbledon, where she reached the final last year.
"I hope so," she said. "I'm still working on it and working on getting there. So I think it will be enough time."
Williams added that she would consider taking a wild card into a grass-court warm-up event.
Osaka's winning run is halted
Naomi Osaka admitted the pressure had weighed too heavily as her winning grand slam run was ended by Katerina Siniakova in the third round.
The world number one had won 16 consecutive slam matches dating back to a third-round loss against Angelique Kerber at Wimbledon last year, taking in titles at the US Open and Australian Open and two victories here.
But she had been living extremely dangerously, and against Czech Siniakova, the world doubles number one and ranked 42 in singles, she could not find a way back, losing 6-4 6-2.
In her first two matches, Osaka had lost the opening set against Anna Karolina Schmiedlova and Victoria Azarenka before digging herself out of a hole.
This time a comeback never looked on the cards, and a tally of 38 unforced errors made for unhappy reading.
Asked how disappointed she felt, Osaka said ruefully: "It would go from one to 10 and I'm like at a 100 right now.
"Definitely I think this tournament, I have had a feeling that was different to the other grand slams. Usually I find it very freeing and fun, and this time around I was kind of tense the entire time.
"I just feel like there has been a weight on me, and I know that's because everything is sort of new. I have played the French Open before but not in this situation.
"So it hasn't been the happiest of times. Other people outside of tennis, they look at the rankings, like, 'Oh, she's supposed to win this match because the other girl is ranked five million hundred' or whatever.
"These people, they're really good but they have ups and downs. I wasn't ranked one last year. I was ranked 70. There are people that can play really good but not consistently and there are times they shine."
The pressure had not just come from outside, though, as Osaka said in Australia she was already thinking about winning all four grand slam titles this year.
"It's weird but I think me losing is probably the best thing that could have happened," she added. "I think I was overthinking this calendar slam.
"This is something that I have wanted to do forever but I have to think about it like, if it was that easy, everyone would have done it. I just have to keep training hard and put myself in a position again to do it hopefully."
Siniakova to face Keys
Siniakova next faces American Madison Keys, who battled to a 6-3 6-7 (5) 6-4 victory over Anna Blinkova.
World number one Simona Halep had dropped sets in both her opening two matches but needed only 55 minutes to breeze past Lesia Tsurenko 6-2 6-1, the Ukrainian failing to hold serve during the match.
Halep's next test will come against Polish debutant Iga Swiatek, who only turned 18 on Friday and continued her superb tournament by beating Olympic champion Monica Puig 0-6 6-3 6-3.
Swiatek won the girls' singles title at Wimbledon last summer.