Emirates Racing Authority said Monterosso, owned by Godolphin Racing, was found to be lame in his left front leg.
No horse has won the World Cup twice in its previous 17 runnings and Monterosso, a 6-year-old son of Dubawi, was given a fair chance of ending that drought.
Mickael Barzalona, who was to have ridden Monterosso, instead will replace Kieren Fallon aboard another Godolphin runner, African Story.
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