(CNN) -- Russia's Dinara Safina saw her chance to claim the top spot in the women's world rankings disappear with a shock 6-7 6-1 6-3 defeat to eighth seed Victoria Azarenka at the WTA tournament in Indian Wells, California.
Azarenka signals to her coach after completing her victory over top seed Safina.
Safina, who needed to reach the final to leapfrog Serena Williams at the summit of the rankings, blew a 3-1 lead in the deciding set to crash out to the 19-year-old from Belarus.
Azarenka broke the top seed three times in succession for the best victory of her career as she reached the semifinals of a WTA top tier event for the first time.
A tearful Azarenka told the official tournament Web site: "I was almost losing it, but I pulled it off, so I was just very happy because I was fighting from the first to the last moment."
Her only defeat this season, which includes tournament wins in Brisbane and Memphis, came to Serena Williams in the fourth round of the Australian Open where she was forced to retire after feeling dizzy in the extreme heat.
Serena, who went on to thrash Safina in the final to win the first grand slam of the season, and sister Venus are sitting out the current tournament.
In the semifinals, Azarenka will face her doubles partner and fourth-seed Russian Vera Zvonareva, a 6-4 6-2 winner over Denmark's Caroline Wozniacki in an earlier match on Wednesday.
Defending champion Ana Ivanovic of Serbia plays Sybille Bammer of Austria with Poland's Agnieszka Radwanska facing Russian Anastasia Pavlyuchenkova in the second set of quarterfinals on Thursday.