Hurdling great Big Bucks\' chances of adding a fifth World Hurdle title at the Cheltenham Festival next March were labelled as extremely doubtful by his trainer Paul Nicholls after he suffered an injury. Big Bucks - who was due to attempt to extend his record unbeaten run to 19 at Ascot this Saturday - will be joined on the sidelines by another Nicholls star, highly-rated steeplechaser Al Ferof. \"I have some bad news to report,\" Nicholls revealed in his column for a spread betting firm. \"At evening stables tonight (Monday), we discovered a problem with both Big Buck\'s and Al Ferof. \"I am not in a position to go into great detail at this point, but I can confirm that Big Buck\'s will not be taking up his engagement at Ascot on Saturday and Al Ferof will not be running in the King George (on December 26). \"And both are unlikely to run again this season.\" Big Buck\'s winning run started at Cheltenham on New Year\'s Day in 2009. He overtook the previous record of consecutive wins of 17 held by Sir Ken in the 1950s on the opening day of the Grand National meeting at Aintree in April.