LOUISVILLE, Ky. --- The rain arrived at Churchill Downs Friday afternoon, adding yet another variable to what is already a mystifying Kentucky Derby.

Now, in addition to the confusion caused by the necessity of comparing form on dirt and synthetic surfaces, there is the prospect of an off track.

Churchill Downs has one of the fastest drying tracks in the nation -- as long as it receives some sun and some wind. So the issue is when the break will come. If drier air and clearing skies arrive by noon or shortly after, the track can be fast for the Derby.

Weather aside, this afternoon's edition of the Run for the Roses looms a wide-open event with a chink in the armor to be found in every contender.

Big Brown, undefeated in only three career starts and the very impressive winner of the Florida Derby, will have the disadvantage of breaking from the extreme outside post position. Supporters of the colt will point to the fact that he was in the outside starting stall in the Florida feature and skipped to the lead immediately, never looking back.

But Gulfstream Park is a speed-favoring track; Churchill Downs is not.

Nonetheless, trainer Rick Dutrow has exuded confidence ever since arriving in Louisville earlier in the week.

"I'm sitting on go here," Dutrow stated. "We're ready."

Second choice Colonel John also appears ready, having galloped strongly over the track following a blazing work of :57.4 seconds last Sunday.

Detractors of the Colonel point to the fact that all of his starts have come on synthetic surfaces.

"I've liked what I've seen since I got here and I have no reason to change my opinion," said trainer Eoin Harty.

Third choice Pyro is the real mystery horse of the field and will put the handicapping theory of throwing out the last race to the test.

A model of consistency and class until recently, Pyro placed himself in position to be the Derby favorite by winning the Risen Star Stakes and the Louisiana Derby on the Derby trail.

But when he made his debut on Polytrack at Keeneland three weeks ago, he was beaten more than 11 lengths and showed absolutely nothing throughout the race.

Detractors point out that Derby winners usually run well, even if they don't win, in their last prep. No Derby winner in the last 50 years has raced as poorly as Pyro in its final tune-up. The colt's supporters respond that the Derby is run on dirt, not Polytrack.

So, while this Derby may be won by a favorite, it also appears open to being won by a longshot. Practically all of them have a chance. Among those seeming to have a better chance are Tale of Ekati, an astonishing 44 to 1 in the early Friday wagering, Court Vision, currently 14 to 1 and Cowboy Cal, carrying current odds of 39 to 1.

Tale of Ekati won the Wood Memorial catching last year's two-year-old champion, War Pass in deep stretch. The pace in the Wood was fast and the finish was slow, but trainer Barclay Tagg's colt showed sharp improvement in that outing and has trained forwardly since.

Court Vision was third in the Wood and drew criticism for not getting up, but he also seems to be moving forward since that outing.

Trainer Bill Mott equipped him with blinkers and the son of Gulch responded with two very sharp workouts.

The colt will wear the hood this afternoon and, having won the Iroquois Stakes at Churchill Downs last year, bears watching as a horse which likes the course.

Cowboy Cal is consistent as the day is long with three wins and two seconds on synthetic tracks.

However, in his debut at Saratoga, he raced poorly. Second in the same Blue Grass in which Pyro burned, supporters of Stonerside's colt believe his inexperience was more responsible for the Saratoga result than dislike of the dirt track.

"Ideally, he'll find a stalking position," trainer Todd Pletcher suggested. "His last work (five furlongs in 1:00, galloping out six in 1:12) was exceptionally good. I believe he's sitting on a big race."

Trainer Larry Jones, who saddled Hard Spun to finish second in last year's Derby to Street Sense, will go for a unique Kentucky Oaks/Derby double when he saddles the filly Eight Belles this afternoon.

While two trainers, "Derby Dick" Thompson and Ben A. Jones have won both the Oaks and Derby in the same year, neither won them with two fillies. Jones tightened the girth yesterday on Oaks winner Proud Spell and has Eight Belles tuned to try the boys this afternoon.

Eight Belles is sure to be the sentimental favorite this afternoon.

In this Derby, sentiment may be as profitable handicapping tool as anything else.