Venus Williams suffered a shock elimination at the Cincinnati Masters after crashing out to qualifier Ashleigh Barty.
The 21-year-old beat Williams 6-3, 2-6, 6-2 for the first win of her career against one of the world’s top 10.
It was an error-prone performance from Williams after the 37-year-old served up six double faults, with Barty taking advantage to secure a third round encounter against Caroline Wozniacki.
The Australian said: "It's an honour to walk out on the the same court as Venus, to play against her and share the court with her.
.@AshBar96 stuns Venus Williams 6-3, 2-6, 6-2!
— WTA (@WTA) August 16, 2017
"She's a genuine champion of the game and has, I think, paved the way for us young players coming through so to play like I did, I'm really excited."
Barty took the opening set on her fourth opportunity with a clean forehand winner, but then Williams comfortably levelled proceedings by coasting to the second set.
But the 37-year-old dropped her serve in the third and fifth games of the final set, with Barty serving out to love to seal the match.
Williams wasn’t the only high-profile casualty after former world number one Angelique Kerber succumbed 6-4, 1-6, 7-6 to Ekaterina Makarova.
— Ash Barty (@ashbar96) August 16, 2017
But world number one Karolina Pliskova was a comfortable winner after a straight-forward 6-2, 6-3 win over Natalia Vikhlyantseva.
Sixth seed Wozniacki reached the last 32 by beating Russia’s Elena Vesnina 6-2, 6-4, while eighth seed Svetlana Kuznetsova also progressed after a 6-3, 6-4 triumph against Yulia Putintseva.
Other winners included Madison Keys, Dominika Cibulkova, Julia Goerges, Carla Suarez Navarro, Camila Giorgi and Anastasija Sevastova.