The trainer of the Golden Slipper horse with the best record in the wet is expecting a predicted rain-affected track to negate the chances of key runners in the $3.5 million race.

Michael Hawkes, the co-trainer of firming second favourite Mossfun, has been on radar watch for most of the week.

And so it seems has one TAB punter who placed $50,000 on the filly at $4.80 as it started to rain in Sydney on Friday afternoon.

With a forecast for up to 10mm of rain, it all but ensured the world's richest two-year-old at Rosehill on Saturday will be run on a track rated no better than slow.

It only enhances the prospects of Mossfun who is unbeaten in two starts in the going. She had firmed to $4.60 on Friday afternoon with long-time favourite Earthquake at $2.70 with the TAB after as much as $3 was bet at the call of the card.

"Either wet or dry I think she's got a great chance but if the track is rain-affected it just takes a few more out of play," Hawkes said.

"Everyone likes to see a fair surface in racing but obviously we'd like rain because it helps us and the rest of the field has to catch up."

Mossfun is one of only three Slipper runners to have won in the wet.

Darley filly Earthquake has compiled her unbeaten record on dry tracks and the team behind her Golden Slipper campaign admit they are uncertain about her ability to cope with anything worse because of her breeding.

"Her dam Cataclysm has left some lower-quality horses who have wet form but they are by (proven wet track sire) Commands," Darley bloodstock manager Jason Walsh said.

"My impression is the progeny of Commands are more likely to get through the wet than the progeny of Exceed And Excel."

Hawkes Racing is chasing its first Golden Slipper as a training partnership which includes two-time winning Slipper trainer John Hawkes.

The Sydney and Melbourne racing operation has swept all before it in 2014, highlighted by a run of eight wins in stakes races last month.

Hawkes snr trained Cataclysm to win four races during his time at Crown Lodge and his son rates her Blue Diamond Stakes-winning daughter as the Slipper's benchmark horse.

"I know Earthquake might have had a bit of a hiccup at the start of the week but if she brings her A game, which she has always done, I think she's probably the horse to beat," he said.