England's world champion Nick Matthew admitted today that he will be unable to compete in this week's ATCO PSA World Series Finals, the flagship PSA World Tour event in London which features the eight players who earned the most points from the nine PSA World Series championships in 2011.

The $110,000 event will take place for the third time at The Queen's Club, from 4-8 January.

The 31-year-old from Sheffield, who topped the world rankings throughout last year, is still undergoing treatment for the adductor injury sustained during last year's Kuwait PSA Cup - and which later caused him to pull out of the Punj Lloyd PSA Masters, the last World Series event of the year in India in December.

"Worst kept secret in Squash - but have officially decided to withdraw from the World Series Finals this week in London," tweeted Matthew this afternoon.

"The injury, however, is coming along nicely & I hope to be 100% by the Tournament of Champions in New York c/20th Jan," added the world number two, who reached the final of the 2010 World Series Finals at Queen's.

Matthew will be replaced by Dutchman Laurens Jan Anjema, the world No9 from The Hague who will be making his debut in the championship.

"Just got the message that due to Nick Matthew's injury, I will be playing the World Series in London on Thursday," Anjema said on Twitter. "Very excited!!"

The six-time Dutch national champion will begin his campaign against Gregory Gaultier, the world No3 from France.

Matthew's announcement follows last week's news that former champion Ramy Ashour will also be on the sidelines as the result of a hamstring injury. The 24-year-old from Cairo, champion in 2007, finished in third place in the 2011 Dunlop PSA World Series Standings after winning three World Series titles in the year.

First Pool round line-up (Wednesday 4 January):
1800: Group 1 - James Willstrop (ENG) v Karim Darwish (EGY)
1845: Group 1 - Mohamed El Shorbagy (EGY) v Mohd Azlan Iskandar (MAS)
2020: Group 2 - Laurens Jan Anjema (NED) v Gregory Gaultier (FRA)
2100: Group 2 - Amr Shabana (EGY) v Peter Barker (ENG)