Assistant trainer Scott Blasi labelled Curlin's exercise rider Carmen 'Carlos' Rosas "irreplaceable" after he guided the top-rated horse in the world through his Dubai World Cup preparations.

Blasi, number two to Steve Asmussen, insists Rosas' contribution will be key if the American Horse of the Year adds the US$6million World Cup to October's Breeders' Cup Classic triumph on Saturday.

The four-year-old son of Smart Strike has been in Dubai for over a month and won the Jaguar Trophy on February 28 with a stylish weight-carrying performance on his eagerly anticipated UAE debut.

He has also impressed in several workouts at Nad Al Sheba.

"Carlos is irreplaceable," said Blasi after watching Curlin in light exercise on Monday morning.

"Every time I ask him to do something with him it is right on. It is a team effort all the way round.

"He's physically ready to do what we are going to ask him to do on Saturday," Blasi declared.

After winning the Jaguar Trophy, Curlin visited the starting gates at Nad Al Sheba.

He also spent time in the paddock during racing on Super Thursday's March 6 programme before coming through a demanding six-furlong drill on March 17 - a piece of work described as his most significant exercise before the World Cup.

Curlin is being honed in the same pattern used before the Breeders' Cup, and worryingly for the other 12 horses set to run on Saturday, Blasi insists he is now stronger and more mature.

Godolphin's duo of Happy Boy and Jalil, winners of rounds one and three of the Maktoum Challenge, are set to lead the challenge behind odds-on favourite Curlin in the climax to the US$21million Dubai World Cup meeting.

Last year's runner-up Premium Tap, Vermilion, who finished fourth 12 months ago, and Mike de Kock's Asiatic Boy are also set to be in the field for the 10-furlong dirt showpiece.

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