The two horses last battled against each other in the Betfair Chase at Haydock in November.
Long Run was the favourite to win, but Paul Nicholls' 6-1 11-year old silenced critics by winning the Chase for the fourth time.
Nicky Henderson has announced that he expects Kauto Star to be the main threat as he attempts to win the King George VI Chase for the second time.
He claims that six-year old Long Run should race at his best at Kempton.
Stablemate Master Minded seems to be a key player in the mix and he adds to the competitive nature between Henderson and Nicholls.
Boxing day is going to be a great day for all horse racing fans. It is an important day for Henderson as he needs to maintain a challenge to Paul Nicholls.