Horse racing is a gambling sport, and gambling is an act of faith. You have to put it on the line, and you have to believe. Saturday, when the biggest event in New York racing goes off at Belmont Park, will be a celebration of faith, a ritual parade replete with uniforms, flags, and a blast of bugles. Every dollar pushed through the betting windows is a prayer for the future. The majority of bettors will be laying their prayers on the undefeated bay colt named Big Brown, but every horse in the post parade of the $1 million Belmont Stakes, the third and final leg of the Triple Crown, is an invocation of the Fates.

Through the tiny gesture of putting money on his or her idea, the bettor becomes invested in the horse. As an experiment, wait for a race in which your horse flops on the stretch and turn your eyes to the people instead of the horses. The moment is one of religious portent. The fans wish, hope, pray, push for their horse, beg him to get up there. It is a moment far beyond sport. It’s the sort of thing about which one might evangelize.

This is why the best race of the day is always the next one. The greatest horse race of all time is the one that hasn’t yet been run.

RELATED: Casino Drive Scratched at Belmont With Hoof Injury

It’s Friday, we can believe what we want to believe. Sunday, we’ll have to deal with the facts.

Saturday, we have three levels of engagement, three planes upon which the Belmont Stakes will operate. The first is personal and intense, as described above. That the personal rapture of horse racing takes place at the 600-acre Belmont Park with cold beer and barbecue sandwiches is icing on the cake.

The next, bigger bet is whether or not Big Brown will prove that he is the best horse of this 3-year-old crop.

He’s already proven it, of course, he’s already rewritten the past performances of his challengers and made them look like a herd of lackluster plodders. Everyone may act now as if they’ve always known that this crop was a bunch of no-accounts, but a quick scan of handicapper’s picks for the Derby shows that very recently a lot of people who know a great deal about horse racing thought that Pyro or Colonel John would be wearing the roses.

Before the Derby, many handicappers, and in this accusation I must include myself, claimed that Big Brown was too green, didn’t have one or another of the attributes that it took to win the Derby. After he’d won it, they (and here I will emphatically not include myself) said there was no one else running in it anyway. Big Brown won, and those same folks who had touted another horse began chipping away at the victory, by saying that the competition wasn’t that good.

It’s nonsense. He’s run against everything that there was, every 3-year-old the scene has to offer. It would be fun to watch the 11 Triple Crown winners go into the gate together, but that’s not how it works, Seattle Slew didn’t run against War Admiral in the Triple Crown races, he ran against 3-year-olds.

Among 3-year-olds, there’s only one question looming: The interesting Japanese import, the $950,000 brother to Jazil and Rags to Riches (winners of the last two Belmont Stakes), Casino Drive.

The race scenario I see unfolding puts Big Brown and Casino Drive in the front whenever they get tired of running with Da’ Tara — probably on the back stretch heading into the turn — they’ll both still be throttled down, playing for time, and waiting to start running for as long as they can. But the race will be on, and they will steadily notch it up.

They will both have something left in the tank when they turn for home. On the stretch at the Belmont Stakes, and especially by the time they’ve run 1 1/4 miles, most of the horses are through. They drag home many lengths behind the leaders. Big Brown and Casino Drive will leave everyone in the dust.

This is what we’ve been waiting to see. This is where the real story, the third level, the question of horse racing history and the Triple Crown gets written.

Big Brown has not been challenged in any of his stretch runs; he has not, in closing a race, had to keep running. This, to a large degree, is why brilliant handicappers such as Mike Watchmaker are skeptical of his prowess in a historical context.

Casino Drive’s racing manager, Nobutaka Tada, said of his recent workouts (which were slow) that he was after “Acceleration. Slow beginning. Finish fast.”

It’s a good strategy not just for the Belmont, but for beating Big Brown. It’s also a good strategy for those of us who believe that Big Brown will win. Big Brown is 12 furlongs away from a spot in racing history, just shy of two and a half minutes of racing away from his coronation. Casino Drive may be the only question looming among the 3-year-olds, but the bigger question is inside Big Brown.

Big Brown needs to finish, and win, a race under pressure. If he wanders home with another self-satisfied, halfhearted lope, the biggest question on the table — what does Big Brown really have in him? — will go unanswered. Can he rise to a real challenge, stare a good horse in the eye, and shut him down? We’ve seen what he can do, but we still don’t know what he’s got. I can’t wait to find out.

mwatman@nysun.com