Chris Waller has erred on the side of caution and put the best interests of champion mare Winx first in deciding to send the dual Cox Plate winner for a spell.

Winx won her second Cox Plate at Moonee Valley on Saturday, streeting her rivals by a record margin of eight lengths in the $3 million weight-for-age championship of Australasia.

Waller and the mare's owners had considered running her in the $2 million Emirates Stakes (2000m) at Flemington on November 5.

But a slight abrasion on a leg which has been treated with antibiotics, made the decision to send her to the spelling paddock an easy one.

"We've got to be professional with every horse and obviously a horse like Winx, you just don't second guess what the vets say.

"If they say you need some antibiotics, it's got to be administered.

"So that's been done and already we've seen the leg return to normal," Waller said.

"But you just never know where an infection might take. It's no different to people. I can't stress enough how the horse always comes first, whether that's Winx or not."

Waller said the mare's longevity was of utmost importance with big targets again next year including the Queen Elizabeth Stakes in Sydney in the autumn and an attempt at a third Cox Plate.

"You'll see her race at least eight times in the next 12 months, so that's more important than just two weeks when you might not quite be 100 per cent right," Waller said.

Winx's Cox Plate win on Saturday was her 13th straight victory, a winning sequence which began in the Sunshine Coast Guineas in May 2015 and has included nine Group One victories.