Three-time Grand Slam champion Angelique Kerber has lost in the first round of the French Open for the second straight year.
19-year-old Slovenian Kaja Juvan beat the 18th-seeded German 6-3, 6-3.
Kerber held the no.1 ranking. He has won every major title except the French Open. Her best performances were the quarterfinals at Roland Garros in 2012 and 2018.
Two-time Grand Slam champion Svetlana Kuznetsova also went out. The 2009 French Open champion lost to Russian countrywoman Anastasia Pavlyuchenkova 6-1, 2-6, 6-1.
Garbine Muguruza could have joined Kerber and Kuznetsova.
But the 2016 French Open champion held firm to beat Tamara Zidansek 7-5, 4-6, 8-6.