Kim Clijsters has withdrawn from the BNP Paribas Open with a nagging shoulder injury as she retired during her match with France's Marion Bartoli.
After winning the opening set of the fourth-round match, Clijsters called for her trainer at 1-2 before conceding with the score at 3-6 3-1.
Clijsters' exit at Indian Wells ended any hopes the Belgian had of regaining the world number one ranking.
Top seed Caroline Wozniacki defeated Alisa Kleybanova 2-6 6-3 6-1.
Clijsters had to finish higher than the Dane to climb to the top of the rankings.
The Belgian has been taking the painkiller Advil to cope with the injury since before she won her fourth Grand Slam title at the Australian Open in January.
"With those higher shots against the opponent today, I just feel it pinching a little bit more when I have to do that kick serve and when I have to reach that right arm up higher with the forehand," said two-time Indian Wells winner Clijsters.
"It's not that I'm really, really worried about it but it is something that I have to pay attention to and that I don't want to risk."
Wozniacki recovered after a poor start and broke her Russian opponent three times in the final set to seal victory in just under two hours and claim a quarter-final place.
Also in the last eight, 15th seed Bartoli will face 19th-seed Ana Ivanovic, who beat fellow Serb Jelena Jankovic - the defending champion - 6-4 6-2 earlier on Tuesday.
Sixth-seed Jankovic, who beat Wozniacki in last year's final, converted only one of seven break-point opportunities as she was defeated by Ivanovic for the first time in three meetings.
"I felt like my game was not really there. I wasn't really doing the right things out there," said Jankovic.
Meanwhile, Novak Djokovic advanced through to the fourth round with a 6-0 6-1 win over Ernests Gulbis.
The third seed broke Gulbis three times in the opening set and twice in the second to maintain his unbeaten run so far this season.
"I am just trying to play as best as I can, I couldn't have asked for a better start to this year," said Djokovic.
"The last three months have been unbelievable."
In the next round Djokovic, the Australian Open champion, will meet either number 16 seed and fellow Serb Viktor Troicki or the 24th-seeded Frenchman Michael Llodra.
Roger Federer recorded a comprehensive 6-0 6-2 victory over 29th-seed Juan Ignacio Chela of Argentina.
"Especially on a hot day like that, you pick the right days to play well and win quickly, so I'm happy it went so well," said Federer.
"I was able to move him around. Then I was able to mix it up, and I took his options away a bit."
Federer, a 16-time Grand Slam champion, will play 18-year-old wildcard Ryan Harrison in the fourth round of the competition after the American defeated 20-year-old Canadian Milos Raonic 7-6 4-6 6-4.
Seventh-seeded Czech Tomas Berdych crushed 26th-seeded Thomaz Bellucci of Brazil 6-3 6-2 to join Djokovic in the fourth round.
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