Andy Murray now goes through to the finals of the Paris Masters where he faces John Isner.
Britain's Andy Murray became the new world number one on Saturday after Milos Raonic withdrew from their Paris Masters semi-final with injury.
The walkover will see Murray, 29, move to the top of the rankings for the first time in his career after replacing long-time incumbent Novak Djokovic.
Raonic said he had suffered a muscle tear in his right leg in his previous match, sending Murray through to face John Isner in Sunday's final.
"This morning I had trouble waking up and getting out of bed. So I went to sort of clear any serious diagnosis," said Raonic, who hurt himself in Friday's quarter-final win over Jo-Wilfried Tsonga.
"Did some tests. Did an MRI half an hour ago, let's say. They found that I have a tear, Grade 1 tear in the right quad.
"Unfortunately, I'm not able to compete against Andy today in the second semi-final."