Darren Weir is yet to decide if his secret weapon will be heading to Randwick for the Doncaster Mile.

Stratum Star will represent Weir in Australia's toughest 1600m-race on Saturday but the trainer is holding off on whether Peter Ellis is Sydney-bound as well.

Ellis prepares speed maps for Weir's vast number of runners Australia wide and also walks the tracks looking for any advantage.

Weir has acknowledged the input Ellis has had in the success of the stable in recent seasons.

Ellis went to the Gold Coast earlier in the year and was instrumental in Mahuta and Lucky Hussler pulling off a Magic Millions double.

Ideally Weir would like another Peter Ellis as he also has a large team engaged at Mornington on Saturday.

"He can't be at Mornington and up in Sydney as well, so we've still got to work that out," Weir said.

"He went up to the Gold Coast earlier in the year and he'll go wherever I want him to."

Stratum Star heads to Randwick in good order for his assault on the $3 million race but is rated one of the outsiders at $51 behind the dominant $1.85 favourite, Winx.

The four-year-old won the Group One Sir Rupert Clarke Stakes at Caulfield last spring before running third in the Toorak Handicap.

Stratum Star will be lining up for the fourth run of his current campaign.

He finished second to Turn Me Loose in the Futurity Stakes at Caulfield before running third to He Or She and The United States in the Blamey Stakes at Flemington.

"He's in great shape but it's a really good race," Weir said.

"He'll get a great run from the barrier but I just don't know if he's good enough."