Tommy Berry knows a thing or two about the highs and lows of racing.

The jockey was booked to ride Japanese star Tosen Stardom in the Queen Elizabeth Stakes until the horse was forced out of the race because of a bleeding attack.

For Berry it seemed as though his chance to ride in the weight-for-age race had gone.

"I was quite gutted about that," Berry said.

But since then, Michael Walker, who partnered Criterion to placings in last year's Cox Plate and Melbourne Cup, had to give up the Queen Elizabeth ride after fainting and being hospitalised on Sunday.

Walker's misfortune has turned out to be Berry's good luck as David Hayes and Tom Dabernig-trained have called on the Sydney jockey for the $4 million race at Randwick on Saturday.

"I think David Hayes has got him perfect for Saturday," Berry said.

Berry gets on Criterion for the first time in a race at the horse's 36th and final start before the entire retires to stud.

"I rode him in track work on Tuesday morning and he worked really well," Berry said.

"I've done trips to Hong Kong and jumped on horses I've never sat on before in Group Ones and won them so I wouldn't see that as a problem."

It would be a fairytale finish for Criterion, a four-time Group One winner who has earned more than $7.2 million in prize money.

Criterion is rated a $6 chance to end his racing career on a winning note.

The United States is the $4.60 favourite and BMW winner Preferment is second pick at $5.

There is one prize up for grabs on Saturday which would eclipse any Group One victory in Berry's eyes.

The Nathan Berry Medal, named in honour of Berry's brother who died in 2014 from a rare disease, is awarded to the leading jockey over the two days of The Championships.

"It's a pretty special medal. It's close to my heart," Berry said.

"I won it the first year and rode a Group One double on that day as well."

Berry leads the medal on the back of wins in the TJ Smith Stakes, ATC Australian Derby and the Country Championships final last Saturday.