British boxer Nicola Adams' scheduled fight with Hungarian Alexandra Vlajk was called off soon before the start time due to a problem with her Hungarian opponent's pre-fight blood test.
The dual Olympic gold medallist from London and Rio was due to fight Vlajk in a junior bantamweight bout on the Canelo Alvarez- Gennady Golovkin undercard.
But the bout was abandoned just before the fighters were due in the ring.
"I'm devastated that I'm not boxing tonight, due to a problem with my opponent, thank you everyone for your support and kind messages," Adams wrote on Twitter.
Adams jumped at the chance to appear on the high-profile card, hoping to achieve a goal she's held since the days when she would stay up into the early hours to watch her heroes on television.
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But organisers had no choice but to call off Adams' third professional bout.
The Briton had earlier spoken of the excitement of being in the boxing capital of the US.
"To be able to perform in Las Vegas on the undercard of the biggest fight of the year is an honour for me," she said.
