One of the best wet ground records in Australian racing is poised to get even better at Eagle Farm.

The 150mm of rain that has fallen on Eagle Farm during the past week is already enough to ensure Doubtful Jack is one of the main chances in the Tattersall's Members' Cup (1600m).

If there's more before Saturday, trainer Kelly Schweida says the former Melbourne sprinter-miler might be only one of two realistic chances in the $80,000 Listed race.

"If it keeps raining it's going to help him," Schweida said.

"This horse really excels in the heavy going so if it is a heavy track he will be really hard to beat."

Schweida's wish is almost certain to be granted with Eagle Farm already well into the heavy range and showers are forecast for the rest of the week.

Trained by Peter Moody in Melbourne until his mid-season switch to Schweida, Doubtful Jack has four victories from as many starts on heavy tracks.

A combined winning margin of more than 13 lengths in the worst possible going underlines his reputation as a superior wet tracker.

Doubtful Jack won nine races for Moody but he also earned his keep when numbers were needed to ensure Black Caviar had something to race.

A rising seven-year-old, Doubtful Jack twice placed to the champion mare at Group Two level, results which complemented a Group Three win and helped him bank more than $700,000 under Moody's watch.

"He's on the other side of his career but that's probably why he is up here in Brisbane," Schweida said.

Market assessors have settled on in-form Boys On Tour as the horse to beat and Schweida says the $2.10 favourite is an obvious threat to his horse.

"I would think Boys On Tour is the one because he can also handle the wet really well," he said.

Road closures have forced Sydney trainer David Payne to abandon Eagle Farm starts for promising two-year-old Dowdstown Charlie and last-start provincial winner Kimberley Kid.

"We couldn't get a direct trip there with the flooding," Payne said.

"I didn't want an extra four hours added onto the float trip so they are not going."