Shilling (48) performed with credit when he finished ninth equal at the world championships in the United States in 1998. He was the first Otago croquet player to compete at a world championships.
But he battled arthritis and a wrist injury after this and did not play much croquet for the next 10 years.
The Dunedin radiation therapist had limited movement in the index and middle fingers of his right hand, and tried homeopathic and natural remedies in an effort to alleviate the disease.
He had started playing croquet at Wellington College when he was 17.
Ritchie (51), an Associate Professor at the University of Otago, made his world championship debut at Palm Beach, Florida, in 2009.
He is New Zealand's foremost classical composer and his works are regularly performed in New Zealand and, increasingly, overseas.
Ritchie started playing croquet 15 years ago to give himself a break from music and his academic work.
Ritchie made his international croquet debut for New Zealand A in Australia in 2005.
The favourites for the world championships, which run from April 28 to May 6, are England's world champions Reg Bamford and Robert Fulford, and Australian Robert Fletcher.
Bamford, the defending champion, has won three world titles and Fulford five.
