sentences:  At the PDC World Championships, Burnett was never able to achieve the same kind of results that he had in the BDO or at the PDC World Matchplay.His best results at the PDC World Championship were to twice reach the quarter finals (2002 and 2003), but his world ranking steadily fell afterwards, and by the end of 2006 he had almost slipped out of the top 50.As a result, he had to qualify for all the major PDC tournaments, and failed to qualify for the World Championships for the first time in 2006.