This could be good news for punters looking to back the five-year-old, who is a good-value $17 winning chance with online bookmakers from barrier 11 for the 2040m Group 1 feature worth $5 million.
Indeed, Hayes believes Mr Brightside lives up to his name because he is not one who is easily flustered on big race days.
There aren't too many bigger afternoons than Cox Plate Day, and Mr Brightside is a proven performer in this environment, winning the Group 1 Doncaster Mile on April 2.
His form – and just as importantly his mentality – have been impressive since then.
“His temperament hasn't changed one bit (since winning the Doncaster Mile by half a length),” Hayes told racing.com at the Cox Plate barrier draw on Tuesday.
“He's always been a very relaxed horse with a relaxed manner.
“He parades beautifully. If anything, he's probably strengthened a bit.
“He's looking physically stronger through the shoulder and hind quarter, and I'm hoping he keeps improving because it could be fun.”
The gelding has had a good preparation, winning the Lawrence and Feehan Stakes, before finishing fifth and fourth respectively in the Underwood and a Might And Power Stakes, the latter in a red-hot field.
Mr Brightside has also won both his starts at The Valley, saluting by 4.5-lengths in the Feehan Stakes on September 3.
This gives Hayes confidence his middle-distance star – with champion jockey Craig Williams aboard – can be competitive in a crack field featuring the likes of Anamoe, Zaaki, I'm Thunderstruck and Alligator Blood.
“He's got a great record. He's been very impressive here. He won by 4.5 lengths and he really had a good turn of foot on the corner,” he said.
“I think he really accelerates off it, and I think everyone saw that this morning.
“He was very lazy down the back, and when Craig asked him to go he picked up the bit really quickly and ran home in 24.1 seconds.
“So we couldn't be happier with how he's going. I think he put the writing on the wall last start and ran really strong through the line.
“He's not too far off the top three in betting. So we're very hopeful.”
Hayes said a wet track and a wide lane could play into Mr Brightside's hands.
“The way our horse has trained on, the way he handles The Valley, he doesn't mind wet tracks – I can see him being a genuine top-three chance,” he said.
“We didn't get much of a choice (being drawn last), but barrier 11 was the best option.
“It's going to be interesting because there is rain into the meeting, and it's the 15th race on Friday and Saturday.
“They might be coming down the middle of the track by then, so I don't think 11 is bad.
“We've got Alligator Blood outside us who will roll forward, and there are a couple inside us who could roll forward.
“We could end up in a three-wide line in a lovely spot and we love wet tracks. So I'm praying we get plenty of rain.”
Hayes – who with his brother JD are a very talented young training combination and already with plenty of success on their resumes – said winning a Cox Plate would be the best achievement of his career.
The Hayes and Lindsay Park names have a long and illustrious connection with the race.
Ben and JD Hayes' late, great grandfather Colin ‘CS' Hayes won three titles with So Called, Dulcify and Almaarad, and their father David with Better Loosen Up and Fields of Omagh.
Tony McEvoy also won one with the legendary Fields of Omagh, as the then-head trainer at Lindsay Park.
“Huge (to win a Cox Plate). CS has won one, Dad won one. Tony McEvoy's won one,” Hayes said.
“Lindsay Park has won a lot of Cox Plates, and to be able to be a third-generation trainer with JD and my whole family behind me, it'll be huge.
“It'll be the biggest thing that we've done to date, for sure.”