Four-time Olympic champion Laura Kenny has withdrawn from the UCI Track Cycling World Championships in Pruszkow due to illness.
Kenny won team pursuit silver on Thursday and was due to compete in the omnium on Friday, but Katie Archibald will represent Great Britain in her absence.
She posted on Instagram: "I am absolutely gutted to announce that I won't be riding in the omnium at the World Championships today.
"I haven't been feeling right all week for reasons we're not sure of, but we do know my performances in the team pursuit over the last two days have been well off where I have been in training over the last two weeks.
"I would have given the omnium my best shot and I really wanted to do it but with the depth of the squad it was decided that it was better that I didn't compete and give someone else the opportunity.
"I agree with the decision and I think Katie will do a brilliant job. I wish her, and all my team-mates, the best of luck for the rest of the competition."