Tomorrow will tell, or at least it should tell. Defining moments, so beloved by sports writers, can often produce puzzlingly unclear results but the Curragh's National Stakes should indicate whether the dream of King of Kings as racing's newest superstar still lives or if he can be dismissed as a presumptuously titled colt reduced to ordinariness.

A Group One race over one mile of the Curragh's unforgiving plain. Of course it would be a more potent test if Central Park, a colt whose connections believe has the fire of classic glory glowing in his soul, was opposing instead of being at home in his box nursing a sore throat but even so, King Of Kings will have nowhere to hide. All the talk, all the hype, all the fancy 10 to 1 quotes for the 2,000 Guineas will count for nothing. Tomorrow evening, the maturing two-year-old frame of King Of Kings could still represent a potential new Nijinsky or far more worryingly, a towering, raging disappointment.

Which it is likely to be is maddeningly unclear. In his four races up to now, King Of Kings has thrown up enough contradictory evidence to suggest that even those closest to him are as much in the dark as anyone.

Those four runs, all up the Curragh, could be summarised from first to fourth as brilliant, ok, disappointing and ok. Breeding gurus could point to a similarly declining pattern in the career of King Of Kings' half brother General Monash who won by the length of the Newbury straight first time out, won less impressively next time and was never heard of again afterwards. But King Of Kings is by Sadlers Wells, the world's top sire and a notably brave racehorse. There's no guarantee, though, that he has passed on his own courage to his undoubtedly brilliant son.

Such a suspicion about a still emerging talent may be harsh but it is a widespread one within racing. Lady Alexander is the one horse to have defeated King Of Kings so far, in the Anglesey Stakes, and confirmed the judgment of her rider Pat Shanahan.

"He hadn't impressed me in his previous race and I thought if there was a hole in him, she would find it. I know Christy (Roche) didn't give him a hard race and he was found to be sick afterwards but it proved he wasn't unbeatable in spite of all the hype all year," Shanahan says.

That hype, which after a brilliant eight-length debut success made King Of Kings supposedly something of a good thing for the 1998 Guineas, didn't take into account subsequently worrying displays of drifting around the track in the closing stages of his races, and more importantly a high head carriage that smacked of a horse with his own ideas. That may be just King Of Kings' individual style of running, a sort of equine Michael Johnson, but, in a game where every signal must be taken into account, it's a worry.

RTE's analyst Ted Walsh, like many others, thought King Of Kings was something special first time out but is now more circumspect.

"I don't like that he wears his head high. It's usually not a good sign. There are three reasons for a horse carrying his head high. Maybe he's slightly ungenuine, maybe he has a wind problem and maybe it's just his natural gait. It may be just that but, usually, the other two are more likely," Walsh says. Whatever the reason, it makes Roche's job in guiding him all the more difficult.

"Any jockey will tell you, the further away the horse's head, the better," says Shanahan. "If his head is back on your knee, it's much harder to get them into full motion. Maybe that's just King Of Kings' style but the saying in racing is - if the head is in the air, the horse is ungenuine."

If that is the case, King Of Kings could emerge at the critical stage tomorrow cruising all over his opposition and still get run out of it. All of racing, desperate for a new superstar, will hope that it isn't and that, when Roche asks for the maximum effort, King Of Kings strides clear in the manner he appears capable of.

"I would be slightly worried about his temperament," says Walsh. "The last day he went into the stalls dry and came out white with sweat. In my opinion, he is obviously very good but he is thinking about it. He still has to decide if this racing is a good game or a bad game. He has yet to tell us, but Sunday will tell us."

Should King Of Kings win impressively, something Aidan O'Brien, John Magnier and Michael Tabor evidently feel he is capable of doing, then worries about high head carriage and a possible reluctance to put absolutely everything into winning can be put on the back burner. Maybe the giant has been immature and learning and we will see such a display from a more hardened King Of Kings but while all will hope, very few will be prepared to take very short odds about it.

"Whether he's genuine or ungenuine, we will know after Sunday but I wouldn't be surprised if he's beaten," comments Shanahan while Walsh is prepared for anything. "It wouldn't surprise me if he's beaten and it wouldn't surprise if he won brilliantly," he concludes.

That's the beauty and the trepidation. Either way, it's now up to King Of Kings to live up to his name.