Ten Open Women
Venus Williams has become the French Open's first major casualty as the seven-time grand slam winner fell to a straight-sets 6-4 7-5 defeat at the hands of China's Wang Qiang.
Wang avenged her loss to Williams in the first round at Roland Garros last year.
The 85th-ranked player was also beaten by ninth-seed Williams at Wimbledon a few weeks later and had never beaten Williams before Sunday.
The loss marked the first time 2002 runner-up Williams has lost her opening match there since 2001 and the only time in her career she has lost consecutive grand slam opening round matches.
In an earlier match, Sloane Stephens enjoyed her first grand slam win as the reigning US Open champion by demolishing Dutchwoman Arantxa Rus 6-2 6-0.
It was the American 10th seed's first win at a grand slam tournament since claiming her first major title in New York last September.
She was beaten in the first round of the Australian Open and that result in January was one of eight successive defeats she suffered following her Flushing Meadows triumph.
But if Rus harboured any hopes of pulling off another upset, those hopes were dashed on Sunday in 49 brutal minutes by Stephens.
In other women's games, Elina Svitolina marched through to the second round of the French Open after a tough opening set against Australia's Alja Tomljanovic.
World No.4 Svitolina fell 5-1 behind in 23 minutes but powered back to a 7-5 6-3 victory.
France's Alize Cornet dug deep to recover from a set down to defeat Italian Sara Errani 2-6 6-2 6-3 in a show of powerful baseline hitting.
Estonia's Anett Kontaveit is into the second round after a 6-1 4-6 6-2 victory over American Madison Brengle, as is Ekaterina Makarova, who beat China's Zheng Saisai 6-4 6-1, and Petra Martic, who downed Wang Yafan 6-2 6-3.