Kyle Edmund has been forced to pull out of this week's Argentina Open in Buenos Aires because of illness.
After not playing in Britain's Davis Cup loss to Spain as he recovered from his heroics at the Australian Open, Edmund was scheduled to play for the first time since reaching the semifinals in Melbourne.
But a throat infection saw him withdraw ahead of a scheduled first-round clash with Roberto Carballes Baena on Tuesday.
Edmund is expected to be fit for next week's Rio Open, where a run to the final would see the world No.26 overtake Andy Murray to become British No.1 for the first time.
The change is guaranteed to happen anyway on March 5 after Murray's points for winning last year's Dubai Championships come off.