An injured Victoria Azarenka limped out of the BNP Paribas Open with a second-round loss to America's Lauren Davis.
Third seed Azarenka sounded less than optimistic about her chances ahead of the tournament having not played since the Australian Open because of a foot injury.
It quickly became apparent against Davis, who had never beaten anyone remotely of the calibre of Azarenka, that the Belarusian was far from fully fit.
She struggled with her movement and on serve, double-faulting 12 times, and looked in a severe amount of pain as she crashed out 6-0 7-6 (7/2).
Azarenka has been criticised in the past for retiring during too many matches and hinted when she played through pain at the WTA Championships in Istanbul last year that had been on her mind.
She said: "I wanted to give my best shot. Obviously it was maybe a little bit too early. But I gave a fight. I'm pretty proud of whatever I did today. I think it's pretty good considering what I have been through.
"I want to learn how to go through the tough thing, how to try to do the best in the toughest situation. Sometimes it takes time. It's a process to go through."
The other top names fared better, led by second seed Agnieszka Radwanska, who defeated Britain's Heather Watson 6-4 6-3 a day after celebrating her 25th birthday.
Tenth seed Caroline Wozniacki has a lot of ranking points to defend after reaching the final in Indian Wells last year and she began her campaign with a 6-1 6-3 win over Bojana Jovanovski.
There were also comfortable wins for top-10 seeds Simona Halep, Jelena Jankovic and Sara Errani.
Errani next meets Australian Open semi-finalist Eugenie Bouchard, who eased to a 6-2 6-2 win over Peng Shuai.
There was an overdue win, meanwhile, for Errani's doubles partner Roberta Vinci, who defeated US teenager Madison Keys 6-3 6-3.
Vinci had lost all six of her previous singles matches this season and broke down in tears in her post-match interview.
Doubles was the hottest ticket in town on Friday.
Because the tournament is played over two weeks, the top players feel able to fit doubles into their schedules, and the queues snaked around Indian Wells Tennis Garden as Roger Federer and Stanislas Wawrinka opened their campaign.
The superstar Swiss pair took on sixth seeds Rohan Bopanna and Aisam ul-Haq Qureshi and won 6-2 6-7 (4/7) 10-6 to the delight of the packed crowds on the new Stadium 2.
It was Wawrinka's first tour match since his stunning Australian Open victory in January, and he said: "I feel great.
"I was home after Davis Cup for three and a half weeks. I'm really happy. I think my level is really good and physically I'm ready.
"So I'm really looking forward to my match tomorrow and for the rest of the season, because it's just the beginning.
"It took me time to realise really what I did at the Australian Open. Still when I'm saying that I won a grand slam, it's still strange for me."
Federer was happy to experience the new court, and he said: "It's nice to see the game grow and seeing people coming out and enjoying it. It's great. I really had a great time out there with Stan today."
In singles, Romania's Victor Hanescu set up a second-round clash with second seed Novak Djokovic by battling past Stephane Robert 7-5 3-6 6-4.
It was a bad day for America's men, though, with all four home players losing.