Jockey Craig Williams says Mr Brightside will return in the CF Orr Stakes with a new-found physical presence that matches an imposing race record

Mr Brightside embarks on another autumn campaign in the Group 1 race at Caulfield with Williams declaring the six-year-old a fully developed weight-for-age star.

"When you see him he just looks more mature in regards to being hardened," Williams said.

"He hasn't got any bigger, or any taller but he looks fantastic. He hasn't got surplus weight, he's not fat, he just looks more rounded, more seasoned.

"His muscle definition is a lot firmer. He looks the horse that he is on his form guide."

Williams has been aboard Mr Brightside in 25 of the gelding's 29 starts in an association that started with a Geelong maiden win and continues as an early odds-on favourite against eight rivals on Saturday.

Mr Brightside will chase a fifth Group 1 win at his first start since running second to Pride Of Jenni in the Champions Mile at Flemington in November.

Williams rode Mr Brightside in a jump-out at Flemington last Friday and was happy enough with the gelding's performance to suggest one of his favourite horses can rise to another level.

"We joked about that at Flemington before his run in the Champions Mile and said, because he's always improved, it's going to be scary for his opposition if he does come back and keep improving," Williams said.

Williams said the biggest transformation in Mr Brightside over the past two seasons was a willingness to fight for every scrap in a Group 1 contest.

"It took an international horse to beat him a small margin in the Cox Plate, so he's arguably the best miler to 10 furlongs (2000m) horse we have in Australia right now," Williams said.

"He will improve, I feel, with the run but he's going well enough that he can definitely win on Saturday, and I'm looking forward to riding him."