Paris - Simona Halep's shock quarter-final loss to teenager Amanda Anisimova on Thursday illustrated again that the Roland Garros title is the hardest of all the Slams to defend.
Since 1945, there have only been back-to-back champions in Paris on 11 occasions.
Halep's 6-2, 6-4 loss to 17-year-old Anisimova means that only Margaret Court, Chris Evert, Steffi Graf, Monica Seles and Justine Henin have successfully defended the French Open women's title in the Open era.
Henin was the most recent - and that was 12 years ago.
"Nerves a little bit," said the Romanian third seed when asked to assess her defeat.
"Stressed because I felt that I'm playing well, and maybe my expectations for myself were big today.
"Maybe I couldn't handle the tension in my body so I couldn't play my best and I couldn't move at my best level."
Halep believes that Anisimova could even be a potential champion and become the first player born in the 2000s to win a Slam title.
"I think she has a big chance if she's playing like today without emotions and without thinking about the result.
"She was pretty calm. She showed that she's able to do good things and big things, so I think she has a chance."
Halep, 27, will now turn her attentions to Wimbledon where her best run remains a semi-final spot in 2014.
Last year, she was knocked out in the third round at the All England Club by Taiwan's Hsieh Su-wei despite being the top seed.
"Hopefully I can make a good result. But no pressure. This year is a 'chill' year for me."
Results from the 12th day of the French Open on Thursday (x denotes seeding):
Novak Djokovic (SRB x1) bt Alexander Zverev (GER x5) 7-5, 6-2, 6-2
Dominic Thiem (AUT x4) bt Karen Khachanov (RUS x10) 6-2, 6-4, 6-2
Ashleigh Barty (AUS x8) bt Madison Keys (USA x14) 6-3, 7-5
Amanda Anisimova (USA) bt Simona Halep (ROM x3) 6-2, 6-4