English racing commentator Matt Chapman has questioned the depth of opposition Winx has defeated in her 28-race winning streak ahead of Saturday's $5 million Cox Plate.

Speaking with Racing.com's Jason Richardson at the barrier draw function for the Cox Plate and Manikato Stakes, Chapman said he believes the quality of horses who have lined up to face Winx on Australian shores are inferior to those racing in Europe.

"Back home we feel Winx is beating fairly moderate horses," he said.

"Slightly it was proved in the result with Best Solution, when all the horses Winx had been beaten were stuffed out of sight, although completely different type of race.

"The only link we kind of have to Winx is Highland Reel and everyone will say 'Oh Winx beat Highland Reel'.

"You have to remember, when she beat Highland Reel he was a very young horse, he had hardly done anything at that stage, it was only actually at his next start when he went to Hong Kong, and he became Breeders' Cup and Highland Reel really progressed as he become a four-year-old, it is really hard for us to judge."

Winx currently sits at the top of the Longines World's Best Racehorse Rankings but Chapman fears her position should be threatened by Cracksman, winner of the Champions Stakes at Ascot in England last weekend.

"Hugh Bowman doesn't want to sit 10 lengths or 15 lengths off Benbatl, because this is one of those very strange European horses that seems to run better when he is abroad, back home he would be nowhere near our best horses at a mile-and-a-quarter or a mile-and-a-half horses are which are Enable and Cracksman," he said.

"And Cracksman, some of you might have seen in the Champions Stakes at the weekend, I hate to say this in an Australian room, if the handicappers do their job properly he will now be the best horse in the world, if he is rated on what he did at the weekend."