Mr Brightside will have his final Cox Plate lead-up run on October 12.
Mr Brightside has effectively been ruled out of this year's $5 million Group 1 King Charles III Stakes with the gelding's final Cox Plate lead-up run to be the week prior.
Co-trainer Ben Hayes said he and his brothers had settled on an October 12 run for the seven-year-old, with the $1 million Group 1 The Might And Power (2000m) at Caulfield or the $2 million Group 2 Hill Stakes (1900m) at Rosehill his two options.
Mr Brightside ran second in both the King Charles III Stakes and the Cox Plate last year, when the races were run two weeks apart, but the one-week gap this year makes it a less-appealing program.
Hayes said the preferred option at this stage is to remain in Melbourne for The Might And Power, the race formerly known as the Caulfield Stakes, which Alligator Blood won last year before finishing a close third in the Cox Plate.
"The money is very alluring, but he'd be back and forth (from Sydney) and he can have a simple prep," Hayes said of remaining in Melbourne.
"A bit like Gai (Waterhouse) did with Alligator Blood, he won the Caulfield Stakes and then he ran super in a Cox Plate.
"I think we'll follow that path. Yes, it's less money but it's the best thing for the horse."
Mr Brightside is $2.30 favourite for The Might And Power, having held down the $6 third in King Charles III Stakes betting.
He is an $8 chance in Cox Plate markets, which are headed by Japan's Prognosis ($4) and local star Pride Of Jenni ($4.50), who defeated Mr Brightside by 1-1/2 lengths in last Friday night's Group 2 Feehan Stakes (1600m) at Moonee Valley.
Mr Brightside was beaten a nose by Romantic Warrior in last year's Cox Plate, having finished seventh – beaten 2.6 lengths – in the 2022 edition won by Anamoe.
He rounded out his 2022 preparations in The Might And Power, finishing fourth in the event also won by Anamoe.
That James Cummings-trained galloper became the 17th horse to win both races in the same Spring, emulating champions including Winx, So You Think, Northerly and the horse after whom the race is now named.