"Kerry Packer and I bought 42 of these imported horses between 1982 and 1990 and most of them were not much good."
Overseas-trained and bred horses hold 17 of the first 20 spots in Melbourne Cup betting, including the eight most favoured.
Williams doubted Mount Athos, now $10 equal favourite with Saturday's Metropolitan winner Glencadam Gold, could win the Cup.
"I'm not that keen on Mount Athos, he's no champion," he said.
"I might be wrong - I've been wrong plenty of times."
Williams, who conceded previous Melbourne Cup winners Americain and Dunaden were well weighted with 58kg apiece, has spent more than A$30 million buying imported Cups horses in the past five years.
He said that, while many of them were a waste of money, his squad was in great shape to take on the Werribee-based raiders.
He enjoyed probably his single most successful day on Saturday, winning the Craven Plate at Randwick with Mourayan and races at Flemington with Tanby and Fawkner. He provided the quinella in the pivotal Turnbull Stakes with Green Moon and Seville.
All those horses except Fawkner are on the Melbourne Cup trail.
Williams said the secret to the form of his squad was altitude training.
His trainer Robert Hickmott prepares the team at Mt Macedon, 500m above sea level.
Williams said he found it impossible to prepare stayers at city tracks and Australian staying ranks would be improved if most of the staying sires were based in New Zealand.