What exactly is the "Apollo Curse" and how does it pertain to this year's Kentucky Derby?

The Apollo Curse is simply a long-standing trend bettors believe justifies not backing any horse in the Kentucky Derby that was unraced as a two-year-old. It stems from the fact that no unraced juvenile has won the Derby since Apollo, way back in 1882.

While many "Derby rules" have fallen by the wayside in recent years, the Apollo Curse has proven rather ironclad. A number of very good horses over the years have attempted to overturn more than a century of history to no avail.

For example, Coaltown finished second to his Triple Crown-winning entrymate Citation in 1948, and later on was voted champion sprinter and champion older male. In 1973, Forego ran a distant fourth to another Triple Crown hero, Secretariat, but went on to earn three Horse of the Year titles.

Other good ones that recently attempted to buck history were Curlin and Summer Bird in 2007 and 2009, respectively. Curlin finished third to Street Sense in the Derby, but beat that rival in the Preakness and later won two Horse of the Year titles. Summer Bird finished sixth to Mine That Bird, but defeated that foe in the Belmont Stakes and was later named champion three-year-old.

A change in training philosophies over the past couple of decades has convinced many observers that it's only a matter of time before the Apollo Curse is finally broken, perhaps on a routine basis. It could come as early as this year as two unbeaten colts, Santa Anita Derby winner Justify and Arkansas Derby winner Magnum Moon, figure among the top five betting choices. Justify, in fact, is widely considered to be the likely post time favorite.

The trainers of Justify and Magnum Moon – Bob Baffert and Todd Pletcher, respectively – have both taken legitimate shots in past Derbies with unraced juveniles. The Baffert-trained Bodemeister got as close as any have when finishing second as the favorite in 2012, 1 1/2 lengths behind I'll Have Another.

Pletcher has taken multiple tries at it, most notably with Dunkirk (2009) and Verrazano (2013). Although well backed at odds of 5-1, Dunkirk finished 11th in 2009, while Verrazano, an 8-1 chance in 2013, finished 14th.

With two quality colts and trainers looking to end the hex, the durability of the Apollo Curse will be severely tested this year. 

SCULLY: Apollo casts a long shadow but curses made to be broken

Apollo Photo courtesy of the Kentucky Derby