Three-time champion Venus Williams was dumped out of the Miami Open on Monday in straight sets by Kazakhstan's Zarina Diyas.
Diyas, ranked 89th in the world, had lost her only previous match against seven-time major winner Williams, but saw off the American 6-2 7-6 (12-10).
"I'm very happy with the win, it was very tough," Diyas said after her victory. "Venus, I looked up to her when I was little, she's such a legend. So for me, it's a really special win."
Elsewhere, Shelby Rogers overcame fellow American Madison Brengle 6-3 6-3 to set up a second-round clash with fifth seed Elina Svitolina.
"I'm really happy to get through that one, she's a really tricky player," Rogers said. "It's actually my first win at this site. The last time I was here, I was spectating, as an injured person! So I'm very happy to be here."
There were also wins for Magda Linette, Sorana Cirstea, Barbora Krejcikova and Kaia Kanepi, while Ajla Tomljanovic beat Anastasia Potapova to seal a clash against second seed Naomi Osaka in the next round.