British number one Emma Raducanu put a dampener on Serena Williams' farewell tour after thrashing the American great in the Cincinnati Open first round.
Williams who plans to retire after the US Open, which starts later this month lost 6-4, 6-0 in what is set to be the penultimate event of her career.
The 23-time Grand Slam champion lacked sharpness and her 19-year-old opponent punished her in a composed display.
Reigning US Open champion Raducanu will play Victoria Azarenka in round two.
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