Trainer Dan O'Sullivan will wait until later in the week to decide whether Bendigo Guineas placegetter Truly Discreet runs on a seven-day back-up at Caulfield.

Truly Discreet gained valuable black-type with her third in Saturday's Listed 1400m-race at Bendigo and O'Sullivan has nominated the three-year-old filly for a 1600m-race against her own age and sex at Caulfield.

"I'll probably accept with her and wait until later in the week to make up my mind whether to back her up or not," O'Sullivan said.

"I'm trying to get her to the Australasian Oaks in South Australia on the fifth of May.

"She can run on Saturday and again on Anzac Day, or I'll just wait until Anzac Day.

"We've nominated today and we're going to plan to run on Saturday if she has a good week."

Truly Discreet is by Teofilo and is the last foal out of retired broodmare She's Discreet who gave O'Sullivan his first stakes win in the 1999 Group Three Dermody Stakes in Adelaide.

O'Sullivan said Saturday's Guineas placing was a big deal for the filly and he believed Truly Discreet would be even better next season.

"It's put me on the wrong leg, in some respects, to get to the Oaks in Adelaide but we ticked that box of getting black-type with her, so it was a good result," he said.

He said everything would need to go right for the filly to line up in next month's Oaks (2000m) at Morphettville.

"We'll try to get her there and if we don't, there's a few other mile races over there we can look at," he said.

O'Sullivan said Truly Discreet appeared to have come through the Bendigo race well, and the filly has also proven she can race well on a quick turnaround.

She won over 1500m at Moonee Valley last December on an eight-day back-up.

"It's nice to know she can back up," O'Sullivan said.

Saturday's Caulfield meeting includes the Listed Galilee Series Final (2400m) for three-year-olds which has attracted 26 nominations.