Cyrname inflicted a first defeat over jumps on Altior in a much-anticipated clash at Ascot in the Christy 1965 Chase, while Lostintranslation proved himself a genuine top-class staying chaser with victory in the Betfair Chase at Haydock on the same afternoon.
Nicholls is also set to call upon last year's King George hero Clan Des Obeaux, while Tizzard has a second string to his bow in Thistlecrack - winner of the race in 2016, fourth in 2017 and runner-up to Clan Des Obeaux 12 months ago.
Nicky Henderson's Altior retains the option of stepping up to three miles for the first time, following Wednesday's acceptance stage for the big race.
Willie Mullins has whittled his potential team down to five - with Duc Des Genievres, Footpad, Min, Real Steel and Voix Du Reve all left in - but Chacun Pour Soi, Douvan and Cheltenham Gold Cup hero Al Boum Photo have been scratched.
The confirmation stage is on December 20, at which point horses can be supplemented at a cost of £10,000.