A hamstring strain sustained by Ashour in the World Championship in Doha earlier this month has led to the withdrawal from the PSA World Series Squash Finals of the 25-year-old, who will reclaim the top men’s ranking at the beginning of January.
Ashour beat Sheffield’s defending champion Nick Matthew on the way to the world final, where he defeated compatriot Mohamed El Shorbagy in five gruelling games.
Only the best eight performers from the 2012 World Series events qualify to play in the flagship event at London’s Queens Club, with Ashour’s place now being taken by Germany’s Simon Rosner.
“I am so happy to be in the World Series Finals – something I think that no one from Germany has achieved before,” said Rosner.
“I hope Ramy is not injured too badly.”
Rosner finds himself placed into a group comprising of Willstrop, Egypt’s Karim Darwish and France’s Gregory Gaultier.
Matthew makes up Pool A along with fellow Englishman Peter Barker and the Egyptian pair of Mohamed El Shorbagy and Amr Shabana, the defending champion.
The event, which starts on January 2, sees players playing each other over three days before culminating in the final on Sunday, January 6.
There will be little chance of rest for the eight-strong field with the eagerly-anticipated Tournament of Champions event set to start at New York’s Grand Central Station less than two weeks later.