A hamstring injury sustained in last year’s Saudi PSA World Open has caused Egypt’s world No3 Karim Darwish to pull out of next week’s ATCO PSA World Series Finals in London. Darwish will be replaced in the eight-man field by Alister Walker (pic), the world No20 from England. The Botswana-born 28-year-old will be making his debut in the event. The draw has also been revised, with the players now lining in two pools as follows: Pool A:  Ramy Ashour (Egypt),  James Willstrop (England),  Thierry Lincou (France),  Alister Walker (England). Pool B:  Nick Matthew (England),  Amr Shabana (Egypt),  Peter Barker (England), v  Wael El Hindi (Egypt). The World Series Finals will take place in an iconic inflatable structure, specifically created for the show-piece event. Inside the structure, the ‘Z-Court’ which is made by ASB SquashCourts, will contain the very latest in squash-viewing.