Hong Kong's superstar jockey Joao Moreira looks to have escaped serious injury after crashing heavily in race 4 on Melbourne Cup Day.

Moreira has been ruled out for the remainder of the day - meaning he will miss the ride on Thomas Hobson - after crashing to the turf on the Flemington bend in the 2800m staying race.

Moreira was attended to by ambulance officers immediately after the fall before getting to his feet and walking unassisted to the ambulance.

Apprentice jockey Ben Allen was later confirmed as the replacement rider for the Willie Mullins-trained Thomas Hobson in the Melbourne Cup.

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Trainer Chris Waller said after the race the horse, Regal Monarch, was "not well".

"It looked like he was travelling well and looked to avoid heels or something," Waller said.

"Joao is conscious and has no neck or back pain."

However there is real concern for Regal Monarch following the fall.

He was loaded into a float and escorted to University of Melbourne veterinary clinic for treatment.