Gai Waterhouse could have a challenger in Paul Beshara as the most confident trainer going into the Doncaster Mile on Saturday.

Beshara saddles up Happy Trails, a $26 chance against the Waterhouse-trained favourite Pierro in the $2 million race, and won't hear of his charge being beaten.

It is the third Sydney autumn for the Adelaide horse and trainer with their best results so far a second in the 2011 Frank Packer Plate and third in last year's Doncaster Prelude before a close sixth in the main event.

Happy Trails' major wins have come in Melbourne with the highlight the Group One Emirates Stakes last November.

"He's better than he was before the Emirates," Beshara said.

"I'm confident. If you train a horse and you can't be confident going into a race, you shouldn't be there.

"I think this horse has turned the corner since the George Ryder and he was very unlucky in that when he lost a shoe.

"And he doesn't know who Pierro is."

Happy Trails finished ninth, beaten just 2-1/4 lengths, in the Group One George Ryder Stakes (1500m) last Saturday week won by Pierro.

After losing his shoe, Happy Trails became unbalanced and didn't get going again until the final 50m.

The prospect of rain overnight at Randwick doesn't concern Beshara who says it could be a bonus for Happy Trails who has barrier 14.

"By the time the race is run, it could be to our advantage to be out a bit wider," he said.

"And I'm pretty sure it will rain. It has every morning I've been here at Randwick even if it's not raining anywhere else.

"He goes well on any surface so it's not a concern."

Track manager Nevesh Ramdhani said the surface had improved from a slow seven to a dead five on Friday but predictions are for a storm overnight.

"The forecast, if it comes true, (means) it's going to be a challenging next 24 hours," he said.

"The track has done everything it could do. It's now left to the weather gods to be a bit lenient on us for the next 24 hours."

Beshara's confidence remains intact regarding the rest of the field which has a stellar line-up this year with 13 individual Group One winners in the field.

Collectively they have won 33 Group One races with Shoot Out, Pierro and New Zealander Veyron scoring five apiece.

Shoot Out, Pierro, Secret Admirer, Streama and Norzita are all Group One winners over the Randwick mile but those statistics mean little to Beshara whose instructions to Glyn Schofield will be simple.

"Win," the jockey will be told.

Whether or not things go to plan, Happy Trails will stay in Sydney for another week and a possible re-match with Pierro in the Queen Elizabeth Stakes.