Superstar jockey suffers nasty fall from Cox Plate hopeful

Superstar jockey James McDonald has been thrown off leading Cox Plate hopeful Via Sistina during trackwork on Tuesday.

The pair were working out at Moonee Valley in front of a sizeable Breakfast With The Best crowd when the horse shifted and McDonald tumbled to the turf.

Vision posted to social media shows McDonald falling off the side of the horse, but getting up quickly and then walking off the track with a couple of helpers.

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Via Sistina - rated a $4.50 chance with TAB for Australia's premier weight-for-age race on Saturday - continued running several laps of the track riderless.

The incident will throw the mare's participation in Saturday's $5 million race into serious doubt.

Yulong Investments racing manager Troy Stephens said it was "very unlikely" she will be racing at Moonee Valley on Saturday.

"Very disappointing, we can see her walking back in now and she looks fine which is the main thing," Stephens told SEN Track.

"Just on straightening there she's just tripped over and dislodged James, and she's obviously done a bit of work after that.

"James said on straightening she's just tripped in front of him, and she was lucky she didn't trip (over)... she had that bandage wrapped around that hind leg which was probably spooking her a lot too.https://twitter.com/katewatts_/status/1848452319215817116?ref_src=twsrc%5Etfw

"She's a super mare, as long as she's all right we're happy."

McDonald confirmed that version of events.

"Unfortunately she just tripped over on a loose bit of gear," McDonald said.

McDonald was able to continue riding other horses at trackwork following the fall.

Via Sistina's trainer Chris Waller reported the horse had not been harmed during the incident.

"She doesn't have a hair missing, there is no blood, no skin off," Waller said.

"We've had our vet look over her, the Racing Victoria vet... I've been over her as well and I can't believe (she is OK).

"When I first saw it I feared the worst something tragically might have gone wrong, and you take comfort that that hasn't happened and that she's safe."

Stephens suggested Via Sistina will now be aimed at the TAB Champions Stakes on November 9 at Flemington.

In her past three starts she has won two Group 1 races - the Winx Stakes and the Turnbull - and has earned more than $3.6m for connections across an 18-start career.

Prognosis ($3) and Pride Of Jenni ($4) were the only Cox Plate runners ahead of Via Sistina in the market before Tuesday's incident.