She's already a world champion and a national hero.

Now Black Caviar is being cast as the positive face of Australian sport.

The unbeaten mare's comeback to racing at Flemington on Saturday follows a couple of tumultuous weeks of allegations of a rampant drug culture among the nation's elite sportspeople.

But Black Caviar's trainer Peter Moody believes the star sprinter can get sport back onto the front pages for positive reasons.

"I think it'll be good to see the newspapers with a few positives about sport," Moody said.

"Sport in general has been copping a good kicking, and racing's usually at the forefront of that."

But, as she has in each of her 22 starts, Black Caviar has come along at precisely the right time.

"That's what this filly's about," Moody said.

"Her timing is impeccable, she can bring out racing stories for all the right reasons.

"Let's hope Sunday morning is all positive too."

After this weekend, however, Moody hinted that the racing world might be looking for a replacement for the greatest sprinting thoroughbred of all time.

Despite his belief that the horse known around the stable as Nellie is as good, if not better, than she's been in years, Moody refuses to rule out the possibility that Saturday's race, the Black Caviar Lightning Stakes, could be her last.

"I haven't planned anything beyond Saturday," he said.

"It is definitely a race-by-race proposition. I haven't even discussed a possible program with the owners.

"We all know what the options are, but nothing has been determined or discussed beyond Saturday."

On the face of it though, Black Caviar is ready for the campaign of her life.

She is over the injury she suffered in England last June that almost cost her the perfect record she puts on the line at Flemington.

"She is bigger, stronger and, most importantly, happier than she's been in ages," her trainer said.

"She's in a different frame of mind to when she ran at Ascot. She's a totally different horse.

"She's enjoying herself and that's what I wanted to see."

For Moody, the man who has borne almost as much pressure as his horse, Black Caviar's comeback provides a sense of achievement and personal pride.

But the trainer who is nothing if not frank, said there is another aspect of her return to the track that is particularly satisfying.

"The 10 per cent she's going to earn me on Saturday."