Punters are a forgiving breed.

After running the worst race of her brief career in the Blue Diamond Stakes, Concealer has been well supported to make amends in Saturday's Thoroughbred Breeders Stakes at Flemington.

With early favourite Zamzam coming out and Gloriette and Meridian Star also scratched, Concealer has firmed to be the $3.50 favourite.

Sent out fourth pick in the Blue Diamond, Concealer finished ninth behind the Mick Price duo, Extreme Choice and Flying Artie.

Trainer Tony McEvoy was at a loss to explain the performance in which Concealer finished more than 10 lengths behind the winner.

"None of us saw that coming," McEvoy said.

"I suppose the only thing was that it was the first time she was in a field. It was the first time she was buffeted and maybe she just switched off on us.

"That's all I can put it down to."

McEvoy said heading home after the Blue Diamond his mind was made up that the daughter of Nicconi was heading to the paddock.

But he said when Concealer showed no ill-effects from the run, he decided to press with a view to a start in the Group One Sires' Produce Stakes at Randwick on April 2.

Concealer won her debut over the straight 1000m at Flemington on Melbourne Cup day and trialled impressively over the straight course in the lead-up to her second placing to Samara Dancer in the Blue Diamond Prelude last month.

"Back down the straight, drawn out, she'll get a bit of galloping room and we've seen her down the straight twice and she's been super effective," McEvoy said.

"She'll determine what she does next.

"It'll either be the paddock or off to Sydney for the Sires'."