Top seed Angelique Kerber crashed out of the BNP Paribas Open after being defeated by Elena Vesnina.
The German, who will return to becoming world number one at the end of the week owing to Serena Williams' absence in Indian Wells, has been struggling for form this season following a stunning 2016 and here she was downed 6-3 6-3 by the Russian.
Kerber was two games away from going out in the previous round before battling back to beat Pauline Parmentier, but there was no reprieve against Vesnina, who enjoyed the best win of her career.
She said on her courtside interview shown on BT Sport 1: "I played a really good match, she is an amazing player, such a tough competitor.
"I was a little nervous at the end of the match and I am really happy to have closed it because it means so much to me."
Third seed Karolina Pliskova was the beneficiary of a retirement by Timea Bacsinszky as she advanced to the last eight.
Pliskova was leading 5-1 in the first set when her Swiss opponent called time on the match due to a wrist injury, setting up a meeting with Garbine Muguruza.
The Spaniard won an undulating contest against in-form Elina Svitolina 7-6 (7/5) 1-6 6-0 and will need to become more consistent if she is to prosper against the Czech.
Venus Williams survived a scare against China's Shuai Peng, coming from behind to win 3-6 6-1 6-3, while Zvetlana Kuznetsova dismissed Johanna Konta's conqueror Caroline Garcia 6-1 6-4.
Fifth seed Dominika Cibulkova is out, though, as she was downed 6-4 3-6 6-2 by Russian Anastasia Pavlyuchenkova, who will meet her compatriot Kuznetsova in the next round.
Caroline Wozniacki's impressive year continues as she beat ninth-seed Madison Keys in straight sets.
The Dane, who has already reached to finals on tour in 2017, triumphed 6-4 6-4 to set up a meeting with Kristina Mladenovic.
Mladenovic advanced after a routine 6-3 6-3 success over Lauren Davis.