Star filly Mystic Journey is about to get back to work to build up for a campaign aimed at the Cox Plate which will begin before this season is over.

The Adam Trinder-trained Mystic Journey emerged as a star last campaign, winning twice in her home state of Tasmania before dominant victories in the Group One Australian Guineas and $5 million All-Star Mile at Flemington.

Mystic Journey will return to Trinder's stables from the spelling paddock on Monday.

Trinder has pencilled in the Group Three Bletchingly Stakes (1200m) at Caulfield on July 27 as Mystic Journey's planned return.

That means Mystic Journey will race one more time as a three-year-old before turning four on August 1, having won seven times during 2018/19 including her past six starts.

"She has had six weeks out now and let down really quickly," Trinder said.

"She only had four runs for the preparation so she didn't go out dented in any regard.

"Realistically she could have been back in a fortnight ago. She's just started to look a bit bored and agitated in herself. She's out with Jerilderie Letter at my farm, but just the timing of things I wanted to give her the full six weeks.

"She'll be back in before the cold of winter really kicks in and we're hoping to kick off in the Bletchingly."

Trinder said the Bletchingly followed by the Group One Memsie Stakes at Caulfield would determine the make-up of the rest of Mystic Journey's spring campaign.

She will hold nominations for all the features but Trinder is keen to target the Cox Plate (2040m) at The Valley.

"Our first mindset is Cox Plate," Trinder said.

"So we'll run in those two races and that will suggest as to whether we push forward to that or whether we revise and look at a Golden Eagle in Sydney.

"I think she's going to come back definitely as good, but I'm just hopeful as a four-year-old mare that hasn't done a lot of racing, she might be a little bit better.

"There's the Golden Eagle there that has got a lot of prize money attached to it, but I'm really keen see her at a mile-and-a-quarter.

"She gets back, builds and finishes as we've seen over a mile. I just think out to that next journey range she's going to be a little bit better once again."