A rare leg injury is threatening the career of reigning Australian Horse of the Year Weekend Hussler.Trainer Ross McDonald announced on Wednesday the seven-time Group One winner would not race again this year after failing to recover from the injury sustained when he was unplaced in the Australia Stakes (1200m) at Moonee Valley.McDonald said Weekend Hussler wrenched his off fore fetlock when he jumped at a shadow in the Group One sprint and that the joint had become badly inflamed because of lea

A rare leg injury is threatening the career of reigning Australian Horse of the Year Weekend Hussler.

Trainer Ross McDonald announced on Wednesday the seven-time Group One winner would not race again this year after failing to recover from the injury sustained when he was unplaced in the Australia Stakes (1200m) at Moonee Valley.

McDonald said Weekend Hussler wrenched his off fore fetlock when he jumped at a shadow in the Group One sprint and that the joint had become badly inflamed because of leaking synovial fluid.

The injury, which was discovered by an arthroscope, has veterinary experts baffled and according to McDonald is the first known case in Australia.

"It is a one-off thing and we are still working out which is the best way to treat it," McDonald said.

He said he was unsure if it was a career ending injury.

"It could be," he said. "I can't look in to a crystal ball."

"He is definitely out for the spring. He might just need time."

The son of Hussonet has had a horror season since his all conquering three-year-old year which featured six Group One wins.

Last spring he racked up his seventh Group One win in the Underwood Stakes (1800m) but was luckless in the Turnbull Stakes and failed to stay the distance in the Caulfield Cup.

McDonald planned to target overseas races in the autumn, including the Dubai Duty Free, but a back ailment followed by the joint injury prematurely ended Weekend Hussler's campaign after unplaced runs in the Lightning Stakes and Australia Stakes.

"We gave him time off and he looks great but, unfortunately, he has not recovered," McDonald said.

"We have just got to get the horse nice and sound and then work out where we go from there," McDonald said.

Weekend Hussler has won 12 of his 19 starts and more than $3 million in prizemoney.