Britain’s Emma Raducanu lost her first match as a Grand Slam champion, beaten in straight sets by Belarus’ Aliaksandra Sasnovich at Indian Wells.
World number 22 Raducanu was seeking an 11th successive victory, having won the US Open last month as a qualifier.
But Sasnovich, ranked 100th in the world, beat the 18-year-old 6-2 6-4 in round two of the BNP Paribas Open.
Raducanu, who received a first-round bye, is next scheduled to play at the Kremlin Cup in Moscow in 10 days‘ time.
The Briton was competing without a permanent coach having ended her partnership with Andrew Richardson, whom she has known since the age of 10, after her US Open success.
Speaking after the match, she told BBC Sport: “We had some great memories together – at the US Open and also previous to that – but I’m looking forward to the next chapter and I think that what I am doing right now is definitely the best for me and my tennis.”
Raducanu made an excellent start against Sasnovich – holding to love in the opening game in front of a supportive crowd of about 4,000 for the night session.