Junior added to King George field
Junior leads the field before winning at Royal Ascot
(Healy Racing Photos)
Instead, the David Pipe-trained Junior is the surprise addition to the line-up after connections paid £10,000 to add him to the line-up for the race.
That leaves 15 possibles for next Wednesday's contest, including all of the expected big names such as Long Run, Cue Card, Riverside Theatre, Grands Crus, Kauto Stone and Captain Chris.
Henry de Bromhead had earlier confirmed that Sizing Europe would be staying closer to home over Christmas.
The 10-year-old has looked as good as ever in winning his two starts this season and connections remain keen to test the multiple Grade One winner over three miles on a sound surface.
However, with conditions likely to be testing at Kempton next week, Sizing Europe is set to instead head to Leopardstown for either the two-mile-one-furlong Paddy Power Dial-A-Bet Chase or the Lexus Chase over three miles.
With rain continuing to fall over most of Britain and Ireland, it would seem the shorter race is his most likely target.
Trainer De Bromhead said: "We said at the start of the season we'd love to try him over three miles on better ground, but it doesn't look like we're going to get that at the moment.
"Sometimes you do at Kempton on Boxing Day, but unfortunately we won't this year.
"He has the two options at Leopardstown and we'll leave him in both races , but the way the weather is going at the moment, I would imagine he'll probably run in the two-mile race."
Another Irish-trained horse ruled out of the Boxing Day feature is First Lieutenant.
Mouse Morris scratched his Hennessy Gold Cup third and he will instead head for the Lexus on December 28.
Morris plans to saddle China Rock in the same race, his first appearance since claiming the Punchestown Gold Cup in the spring.
"He's in great form, but we've decided to stay at home with him," said the trainer.
"Leopardstown will be as good a ground as we'll get over Christmas, so we'll go there and see what happens.
"China (Rock) will be there as well. I'm very happy with him at the moment."
Joe Tizzard is confident that Cue Card won't fail for a lack of stamina in the William Hill King George VI Chase at Kempton.