Pierro is at $1.20 for the Caulfield Guineas.
McDonald fashioned an upset in last Saturday's Group One Spring Champion Stakes (2000m) at Randwick when It's A Dundeel defeated $1.28 favourite Proisir from the Gai Waterhouse stable.
"Maybe this one is a little bit different," McDonald said before his ride on Ashokan.
"I had a feeling that he [It's A Dundeel] would upset him [Proisir] and as it turned out he did.
"Pierro, the way he's winning he's a superstar. It's going to make it hard for any of us to beat him but I'm not saying he can't get beaten. It is racing after all.
"He [Ashokan] has been thereabouts without winning but his form is OK."
The New Zealand hoop has been a regular visitor to Australia in the past couple of years but made a permanent move last month to set up a base in Sydney.
"I wanted to ride in the Guineas and I'd love to win a Guineas," he said.
"I haven't won a Group One Guineas before."
He says this spring carnival shapes as his best opportunity yet to win a Group One in Melbourne.
He has won two Group Ones in Sydney, one in Brisbane and one in Hong Kong as well as 10 in New Zealand.
Glass Harmonium ran fourth first-up in the Group One Sir Rupert Clarke Stakes and McDonald will ride him for the first time today.
"I'm looking forward to hopping on him, actually. I think he's pretty well-weighted with 56.5kg for a big horse like him."
Among McDonald's other rides is Temple Of Boom in the Group Two Schillaci Stakes (1000m).
McDonald won the Group One Galaxy at Randwick in April on the Tony Gollan-trained gelding and has also been aboard for two stakes wins at Flemington.
Their horses are fit and well and ready to run the race of their lives.
But none of the trainers lined up against Pierro and Gai Waterhouse in today's A$1 million ($1.25 million) Group One Caulfield Guineas are rehearsing victory speeches.
Pierro and Waterhouse are as formidable a combination as will be seen in any Group One race this spring.
The horse is favourite at $1.26 and his trainer, no doubt, thinks he should be shorter.
"He's quite exceptional," Waterhouse said after Pierro's final Guineas workout this week.
"You'll see that in the Guineas on Saturday."
Pierro is attempting to stretch his unbeaten run to nine in the race that ranks behind only the Golden Slipper - which he's already won - as a stallion maker.
And there appears to be no stopping him.
The trainers of some of the best three-year-olds available will each be rewarded for turning up in the Guineas in which the last of the eight runners receives $20,000.
But the $600,000 first prize seems bound to be added to Pierro's tally of $3.1 million.
John Hawkes, who saddles a horse perfectly named for the Guineas - All Too Hard - believes the frustrations he has endured with the colt this preparation are behind him.
But Pierro is in front of him.
Hawkes said All Too Hard's barrier manners seem to be improved and the distance of the Guineas is right for a colt once rated as Pierro's equal.
"It's just a matter of whether he brings his A game to the races," Hawkes said. "The thing is Pierro does that every time."
John O'Shea runs Ashokan, a colt who could be the one to serve it up to Pierro.
"We'll be aggressive, we won't die wondering," O'Shea said.
"But it's going to be tough."
Leon Corstens, the Melbourne trainer who has produced a couple of the best Guineas winners of the past decade, goes in double-handed against Pierro.
"I'm hoping, but what can you do," he said.
"It would have to go drastically wrong for Pierro to be beaten."
Pierro's closest rival in the Guineas is Epaulette, a colt who has also been his closest rival on the racetrack.
Epaulette ran Pierro to a short half-head at Rosehill in March.
"One of the few positives we can take into it is that we've got closer than anyone else has to Pierro," said Epaulette's rider, Kerrin McEvoy.
McEvoy was exaggerating.
The narrow defeat is the only positive he came up with, and it was really a negative.
There is, however, one glimmer of hope.
Kingston Town, who was trained by Waterhouse's father Tommy Smith, came to the 1979 Caulfield Guineas in much the same manner as Pierro.
He started a long odds-on favourite and finished third.
Waterhouse isn't a better trainer than her father, and there may not have been a better horse to race in Australia since Kingston Town.
-AAP
