Russian Dinara Safina lost her chance to become the world number one when she was beaten 6-7, 6-1, 6-3 by Victoria Azarenka in the quarter-finals of the WTA event in Indian Wells on Wednesday.
The top seed, who would have replaced Serena Williams as the world's top ranked player had she reached the final, was well beaten by the 19-year-old eighth seed.
Safina looked on course for victory when she saved a set point before snatching the opening set on the tie-break, 7-4.
But the wheels came off almost immediately as Azarenka ripped through the second set.
The Russian seemed to have righted the ship when she forged ahead 3-1 in the third, but Azarenka then won five straight games to clinch an upset win.
Azarenka will now play fourth seed Vera Zvonareva, who easily beat ninth seed Caroline Wozniacki of Denmark 6-4, 6-2.
Zvonareva, who reached the last four at the Australian Open in January, won a tight first set and then eased through the second.
In the past, Zvonareva has let her emotions get the better of her, especially in pressure situations, but she said she would not change the way she is on court.
"I think I'm still an emotional player, because I think I like to create on the court," she said.
"I like to play a different game, and I think emotion can help and emotion can harm a little bit.
"I think with experience, I have learned to let the emotions out when I need it, and to focus on myself when I don't need them.
"But other than that, I don't really pay attention to what people say. I think the most important is to stay focused on my game and try to improve. Because I know if I play my game, I can beat anybody."