(Reuters) - Few sports fluctuate as much as horse racing and even fewer races are as unpredictable as the Kentucky Derby.
This year's race, at Churchill Downs on Saturday, is no different and looms as one of the most open in decades.
The early favorite is Orb, who won the Florida Derby, one of the key traditional lead-up races, in brilliant fashion.
His main challenger, at least in betting circles, is the unbeaten Verrazano, but this is anything but a two-horse race.
With a capacity-field of 20 impeccably bred three-year-olds, the 139th Kentucky Derby has all the makings of a classic.
An expected crowd of more than 160,000 will cram into the track while tens of millions of people will watch the race, dubbed the most exciting two minutes in sport, on television.
The only sure bet is that the winner of the Run for the Roses will instantly be feted as the sport's new great hope, raising expectations he can emulate the likes of Secretariat and Seattle Slew by winning the Triple Crown.
But the Triple Crown will have to wait. With no obvious standout horse from this year's field, no one is taking anything for granted before the mile and a quarter race on dirt, one of the toughest tests for a thoroughbred.
Orb was installed as the 7-2 favorite after winning each of his three runs this season, including the Florida Derby, but his trainer Shug McGaughey said he would still need some luck after drawing the 16 hole.
A Hall of Fame trainer who has prepared nearly 250 graded stakes winners but never a Kentucky Derby winner, McGaughey said his prospects could be decided at the first bend.
"Hopefully, he'll get a clean trip around the first turn, which I think is very important," McGaughey told reporters.
"That's where all the jamming up comes. Going down the backside, hopefully, he can ease in and save a little ground, but not be down in there and not be able to make a run when the time comes."
Verrazano, named after the New York City bridge connecting Brooklyn with Staten Island, has won his four career starts, all this season.
He was listed as the 4-1 second pick but has the added weight of history against him.
The last horse to win the Kentucky Derby that did not race as a two-year-old was Apollo in 1882 but Verrazano's trainer Todd Pletcher was unfazed by the doubters.
"As far as Orb being the favorite over Verrazano, that's not an issue. He (Orb) deserves to be the favorite," said Pletcher, who has five runners in the race.
"And it might even be an advantage. There's usually more pressure on the favorite."
Goldencents was rated the next best chance, at odds of 5-1, but none of the 20 runners were longer than 50-1.
His trainer Doug O'Neill won the race last year with I'll Have Another and is hoping history will repeat itself after both horses finished off their Derby preparations by winning the Santa Anita Derby.
Heavy rain is forecast for Saturday's race but O'Neill was unconcerned about the weather.
"From what I know about this track, it handles water real well," said O'Neill. "As long as we don't have any gushers just before or during the race, I think we'll all be all right."
Goldencents is part-owned by Rick Pitino, the coach of the University of Louisville men's basketball team that won this season's NCAA championship.
His jockey is Kevin Krigger, bidding to become the first African American rider to win the Kentucky Derby since Jimmy Winkfield won for the second time in 1902.
Rosie Napravnik is also chasing history in the saddle, hoping to become the first female to boot home the winner. Two years ago, she finished ninth in the Derby, the best placing by a female rider.
Last year, she won the Kentucky Oaks. This time she is aboard Mylute, a 15-1 shot.
The lone international entrant this year is Lines Of Battle, trained in Ireland by Aidan O'Brien, and rated a 30-1 pop.
(Reporting by Julian Linden in New York; Editing by Frank Pingue)