Germany's Angelique Kerber became the first women's top seed to lose in the opening round of the French Open with defeat by Ekaterina Makarova.
Kerber went down 6-2 6-2 in one hour and 22 minutes, leaving her number one status in the balance.
Both Simona Halep and Karolina Pliskova have the chance to take top spot for the first time with good runs in Paris.
However, Halep is recovering from injury and Pliskova fell in the first round last year.
That is symptomatic of the uncertainty in the women's draw that led Halep to claim up to 15 players are in with a chance of winning the title.