Trainer Bjorn Baker wept for his jockey on Thursday, just hours before confirmation Nathan Berry had died of complications from a rare illness.

Baker has trained the $17 chance Unencumbered with a heavy heart since Berry, the only rider to win on the colt, became seriously ill in Singapore last month.

Berry was diagnosed with NORSE disease, a condition which causes severe seizures and brain damage.

He was flown home to Sydney on a special medical flight on Thursday morning and taken to a Sydney hospital where he died in the afternoon.

The 23-year-old's death has cast a pall over the build-up to Sydney's signature horse race.

Baker broke down in front of an audience at a special Golden Slipper breakfast.

He then regathered himself to talk about the sport Berry loved and to declare Darley's second stringer Ghibellines a Slipper wildcard.

"One horse that I think has probably gone under the radar a bit is Ghibellines," Baker said.

Baker ran Windjammer as an outsider last year in his first Golden Slipper experience but he rates Unencumbered, with Craig Williams in the saddle, a "live chance" on Saturday.

Unencumbered will be lining up for his ninth start after winning five times and banking more than $1.8 million but Baker insists the horse still has more to give.

"I think he's had a really good prep," Baker said.

"We've had a break after the Magic Millions ... and I think he'll be peaking on Saturday."

The TAB's Glenn Munsie said Unencumbered had been one of the best-backed horses since Golden Slipper betting opened two months ago.

"Unencumbered is the worst way for us but there is a lot of water to go under the bridge and probably a couple of million dollars to be invested between now and Saturday," he said.

A heavy fog blanketed the final hour of Rosehill trackwork but Michael Hawkes is banking on another weather event to give Mossfun her best chance of winning.

"I'm hoping for a bit of rain, not fog," he said.

Two of Mossfun's three wins have been on rain affected tracks, including a four-length victory in the Silver Slipper.

Earthquake eased from $2.30 to $2.40 in updated TAB betting on Thursday but Munsie said the Darley filly continued to attract support.

Racing NSW vet Dr Craig Suann cleared Earthquake to run in the Slipper late on Wednesday after trainer Peter Snowden had to treat the unbeaten filly with antibiotics for a minor spike in temperature.

"Even with the reports she had the temperature from Sunday through to working yesterday morning she was still the most popular runner with us yesterday," Munsie said.