Surprise update on Cox Plate runner that threw jockey

Champion horse trainer Chris Waller says Via Sistina is all systems go to Saturday's Cox Plate despite her chances looking mighty grim four days earlier.

The mare put a scare through Moonee Valley's $5m feature race when she threw jockey James McDonald during trackwork in front of a large crowd on Tuesday.

McDonald was unharmed but there were immediate fears Via Sistina would be scratched from the Cox Plate, given she ran three laps of the track riderless after losing the jockey.

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

Waller had to change her preparation and took the horse for a swim at St Kilda beach, before doing a canter around Flemington on Friday.

"I'm much happier than I was on Tuesday morning," Waller laughed.

"She's had a good week, simple as that. The workout on Tuesday morning was going well until she parted with James.

"She recovered well, feed bin has been impressive, she has licked it clean every night and day... so she's not suffering in any way.

"This morning she had a very quiet canter here at Flemington... she's bouncing, she really is."

Bookmakers reacted to Tuesday's incident by blowing out the odds on Via Sistina, but by Friday afternoon she had come back in to be a $4.20 chance, behind only race favourite Prognosis in the market.

In her past three starts Via Sistina 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.

Pride Of Jenni was on Friday rated a $4.50 chance behind the other two top contenders.