Aidan O'Brien has announced Ruler Of The World will not run in Saturday's Investec Coronation Cup at Epsom.
Last year's Derby winner, who is jointly owned by Coolmore and Al Shaqab Racing, had his sole start this year in Dubai when only 13th in the World Cup.
O'Brien announced via Coolmore's Twitter feed: "Ruler Of The World worked very well yesterday but pulled out a little stiff this morning so we couldn't risk running him on Saturday."
Earlier Harry Herbert, Al Shaqab's racing adviser, said: "Ruler Of The World worked very well on Tuesday, I was there to see him myself, but unfortunately he isn't quite right this morning and I am almost certain he isn't going to run on Saturday.
"It's bitterly disappointing and very frustrating as everyone was very pleased with the way he worked, but he isn't right this morning and you can't line up in a race like the Coronation Cup unless you're 100 per cent.
"We don't think it's anything serious, Aidan thinks he may have tweaked a muscle. It's too early to say (where he will run next). We hadn't looked beyond Saturday."