Nicola Adams' fight with Hungarian Alexandra Vlajk was called off shortly before the start time last night because of a problem with her opponent's blood test.
The double Olympic gold medallist, from Leeds, had been due to take on Vlajk in a junior bantamweight bout on the Canelo Alvarez vs Gennady Golovkin undercard in Las Vegas but it was called off shortly before she was due in the ring.
Adams wrote on Twitter: "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 jumped at the late chance to appear on the high-profile card, hoping to realise an ambition she has held since the days when she would stay up into the early hours to watch her heroes on television.
It would have been her third bout since turning professional.