LOUISVILLE, Ky. - Hot pace. Muggy day. One of the deepest, talented fields in years.

A delicious stew with all the ingredients for an unpredictable Kentucky Derby.

The 20-horse field for today's race (post time 3:24 p.m., KHQ) is so stacked that unbeaten Gemologist is no better than third choice on the morning line.

In other years, the colt would be the talk of the Derby. In this one, early favorites Bodemeister and Union Rags have grabbed the spotlight.

Still, some very talented colts could go off at big odds - I'll Have Another at 12-1 or, at 15-1, Take Charge Indy, whose jockey Calvin Borel has brought home long-shot winners twice in five years.

"This is the best bunch I've seen in a long time," four-time Derby-winning trainer D. Wayne Lukas said. "I was out there riding next to some of them, and let me tell you, this is a hell of a group."

Lukas will saddle one of the longest shots, 50-1 Optimizer.

"History tells us that you can't throw anyone out," said Todd Pletcher, a former Lukas assistant who has two Derby starters including Gemologist. "There have been some winners the past few years that have been way down everybody's depth charts."

Some of the strongest contenders - Hansen, for example - have had the most success running at or near the pace. But their task is complicated by the presence of speedball Trinniberg, who could prove to be enough of a pest on the front end to compromise any horse willing to keep pace with him.

If the early fractions in the 1 1/4-mile race are fast enough, it could set up well for a deep closer like Dullahan, Daddy Nose Best or I'll Have Another.

Three-time Derby winner Bob Baffert, who trains 4-1 favorite Bodemeister and long shot Liaison, called it "one of the toughest Derbys I've been in probably the last 10 years."

"I've brought some really good horses here, and they were the best horse, but they got beat," he said, referring to Lookin At Lucky, the 2010 race-day favorite who was trapped on the rail and finished sixth. In 2001, his heavy favorite Point Given wound up fifth.

Today's forecast calls for a high of 86 with a 30 percent chance of showers and thunderstorms. The Derby day temperature has topped 80 degrees just five times since 1969, when it hit 87.

Making it feel subtropical is the humidity, which was close to 70 percent on Friday. The heat combined with humidity affects horses in different ways. Some sweat profusely; others handle the elements. All Derby horses will be examined by vets on race morning.