Trainer Tim Glyshaw admits the big guns will have to run below-par if Bucchero is to emerge victorious in the King's Stand at Royal Ascot on Tuesday.
The six-year-old American challenger is 25/1 with Sky Bet for the five-furlong Group One on the opening afternoon of the showpiece meeting.
His compatriot Lady Aurelia is back to defend her crown for Wesley Ward and disputes favouritism with the Charlie Hills-trained Battaash.
Bucchero was in action during an international challengers press morning in Newmarket on Thursday and Glyshaw reported his charge in fine fettle, whilst being realistic about his chances.
Glyshaw said: "It was great for Bucchero to get an invitation and to have a shot at a race like this is a pretty big deal for our stable as we only have just over 20 horses. He's doing really well and he's going to go out there and run his race.
"Battaash is a really nice horse and Lady Aurelia is also a really nice horse who loves Ascot. I think they must not run their A-race and we have to run our best race if we're going to win."
He added: "There is a question about him not running on Lasix and running over the straight track for the first time, but these questions can't be answered until after the race. He does need a little bit of luck. He could run really well and finish fourth or he could run really well and win the race."