Venus Williams was edged by Elena Vesnina in the BNP Paribas Open quarter-finals as Kristina Mladenovic also reached the last four.
Williams, a seven-time grand-slam champion, went down to fellow seed Vesnina 6-2 4-6 6-3 at Indian Wells on Thursday.
The American gave up an early break in the third set before falling 5-2 behind, and she saved three match points in the eighth game.
A lengthy ninth game followed as Williams squandered six break points before Vesnina completed her win.
MLADENOVIC UP NEXT
Awaiting Vesnina in the last four is Mladenovic, the Frenchwoman battling past Caroline Wozniacki 3-6 7-6 (7-4) 6-2.
Mladenovic, a title winner in St Petersburg and finalist in Acapulco already this year, continued her good form.
The 28th seed came from a set and a break down to get past 2011 champion Wozniacki, beating the Dane for the first time in four meetings.
She will need to do similar against Vesnina, who has won their only two previous matches.
Karolina Pliskova will face Svetlana Kuznetsova in the other semi-final at the WTA Premier event.