Nicky Henderson’s star made it 17 wins from 20 starts earlier this month with a stunning victory over dual Champion Chase hero Energumene in the Clarence House at Ascot.
That cemented Jonbon at the top of the betting for the Wednesday feature at the Cheltenham Festival, a race he missed last year as Henderson’s Seven Barrows yard was hit by illness.
Jockey Nico de Boinville dominated from the front in the four-runner contest at Ascot, but his former weighing-room rival Brennan thinks things will be tougher in March.
Speaking on the Unbridled podcast, Brennan said: “I look at Jonbon and I thought it was a brilliant ride in a race like that with four runners where he is able to dictate.
“Come the Champion Chase, it won’t be as easy for him. If he’s ever beatable, it will be that day.
“With the likes of Matata and Il Est Francais, it’s going to be a different ball game.