Johanna Konta will miss this week’s clay-court season opener in Charleston because of a shoulder injury and illness.
The 25-year-old has revealed she was battling both during her run to victory in last week’s Miami Open.
Now seventh in the world, she would have been the highest-ranking player competing in this week’s event.
“[Charleston] is a great tournament and I was really looking forward to taking part,” said Konta.
“I was battling a slight shoulder injury and sickness during Miami which has taken hold since the end of the tournament.”
Konta beat Denmark’s former world number one Caroline Wozniacki 6-4 6-3 on Sunday to become the first British woman to win the Miami Open.
It was her third WTA title and second of 2017.
Her withdrawal means American world number 11 Madison Keys is now the highest-ranked player for Charleston.
Australia’s Sam Stosur and American Venus Williams are also both taking part.