The Colin Tizzard-trained pair have dominated the pre-race discussion ahead of today’s spectacular.
Cue Card edged out the ill-fated Vautour in a thriller 12 months ago and looked better than ever when landing his third Betfair Chase at Haydock last month.
Thistlecrack, last season’s all-conquering staying hurdler, has won each of his three starts over fences with the minimum of fuss under Tom Scudamore, but while Brennan respects his opponent, he is in bullish mood.
Speaking in his 32Red blog, the jockey said: “If Cue Card runs up to his best and Thistlecrack still beats us in the King George, I will never have ridden against, or seen, a better horse. I genuinely believe that.
“And that includes the likes of Kauto Star and Denman, who I know all too well from my Imperial Commander days.
“OK, Thistlecrack may not have to run to the spell-binding level of form that Kauto Star did when winning one or two of his King Georges - though he may have to - but if Colin’s horse can come out best given his inexperience he will have to be one of the best we have seen in a long while.
“Cue Card has an official mark of 176 but I am sure his best performances can be rated higher and nearer 180, so it will be one hell of a feat from Thistlecrack if he can beat us if we are on our A-game.
“Racing can be a great leveller and if we are beaten then so be it. But I will be going out there on Boxing Day thinking I am on the best horse and not expecting defeat. I can’t wait.”
Running your two best horses against each other is never ideal, but Tizzard is looking at it from another perspective and believes he now has twice as much chance of winning one of National Hunt racing’s most prestigious prizes.
Supporters of one of the two superstars will be disappointed, but as both are owned by different camps, the clash was inevitable at some stage.
“I always say in a race like this if you’ve two runners, you’ve twice as much chance of winning. They’ll probably be first- and second-favourites, so let’s have it,” Tizzard told At The Races.
“I think they’ll probably sit third or fourth together. It’s always a ferocious race. Josses Hill coming in is lovely, as we could do with something setting a good, fast pace.
“In the race, Cue Card probably wouldn’t go on until three of four out, but if Thistlecrack is travelling well there’s no reason for him not to go on. He can be ridden any way we want, it will be down to Tom Scudamore on the day.
“Cue Card has been there and done it, he’s rated 176, he’s been brilliant since Haydock and Wetherby brought him on a lot.
“We all know what Thistlecrack can do and he hasn’t been extended for a while. We don’t know what’s left in the engine, he hasn’t beaten a horse of Cue Card’s calibre yet, but who’s to say he won’t?
“We always said if he was going to go to Cheltenham as an also-ran he’d switch back to the World Hurdle, but he hasn’t looked like that yet, he’s looked equally as good over fences.”
Tizzard’s son Joe was stable jockey for many years until his retirement and is now assistant trainer.
He is quite glad he has been spared making a decision between the two as he says he simply cannot split them.
“It wasn’t a particularly tough decision (to run both), it was discussed in depth but ultimately it came down to the owners in the end,” he told Coral TV.
“Dad and I were happy to go along with it. In an ideal world you wouldn’t want the two of them taking each other on, but that doesn’t happen when you get to their standard.
“You can keep them apart if they were running in novice hurdles, but there’s only one King George a year and they both deserve to be running in it.
“I have no idea how it will pan out. I’d hate to have to decide to ride one of them, as I just don’t know.
“Cue Card was every bit as impressive as he’s ever been at Haydock last time and is in beautiful form.
“We’ve not got to the bottom of Thistlecrack. The Newbury performance was the best I’ve ever seen from a novice.”