Kentucky Derby: Is the Apollo Curse a negative or positive?

For over a hundred years, the “Apollo Curse” was a seemingly unbreakable Kentucky Derby handicapping rule.

In 1882, Apollo became the first horse who did not race as a two-year-old to win the Kentucky Derby. His feat went unmatched throughout the 20th century; it seemed juvenile racing experience was basically a prerequisite to win the Derby.

Then in 2018, future Triple Crown winner Justify broke the Apollo Curse with a resounding Kentucky Derby triumph. Five years later, longshot Mage became the third horse without juvenile experience to win the Derby.

This raises an important question for Kentucky Derby handicappers: is the Apollo Curse shattered and irrelevant? Is a lack of juvenile racing experience actually a detriment in the Kentucky Derby, or is the Apollo Curse a myth resulting from an insufficient sample size of horses?

There’s no reason to speculate on the answer. Let’s dig into the data and find out.

Apollo Curse research methodology

The complete racing records of Kentucky Derby starters from the race’s early decades are not readily available. However, a complete list of every Apollo Curse qualifier since 1937 has been compiled by Churchill Downs, so we’ll focus our study on the years 1937-2024.

Since 1937, 75 horses who did not race at age two have competed in 46 editions of the Kentucky Derby. They faced off against 718 horses who did race at age two.

The fact horses who raced at age two vastly outnumber horses who did not among Kentucky Derby starters is a compelling clue that juvenile racing experience makes a horse more likely to achieve Kentucky Derby glory.

But that doesn’t necessarily help handicappers analyzing a Kentucky Derby field featuring one or more Apollo Curse qualifiers. The horses are here, they’ve qualified—the question is, how will they perform?

That’s why we’re emphasizing a more specific question: based on the number of starters in each category, when Apollo Curse qualifiers square off in the Kentucky Derby against horses with juvenile racing experience, are the Apollo Curse qualifiers more likely or less likely to win or finish in the top three?

Apollo Curse data analysis

The results of our research paint a vivid picture:

Horses who did not race at age two represented 9.5% of starters in our sample size of 46 Kentucky Derbys. If all else were equal, one might expect them to record 4.3 wins (9.5%) and about 13.1 top-three finishes (9.5%).

But that’s not what happened. The two wins from Justify and Mage gave the Apollo Curse qualifiers a 4.3% win rate, 55% lower than expected. The group also underperformed at recording top-three finishes; only 10 of the 138 top-three finishers in the sample size were Apollo Curse qualifiers, which means they secured 7.2% of top-three finishes—24% lower than expected.

In contrast, the 718 Kentucky Derby starters who did race at age two represented 90.5% of starters in the sample size. They won 44 Kentucky Derbys (95.7%) and recorded 128 top-three finishes (92.8%), in both cases outperforming expectations.

There’s another way to look at this data. In our sample size of 46 Derbys, Apollo Curse qualifiers recorded two wins and 10 top-three finishes from 75 starts, which means 2.7% of them won and 13.3% finished in the top three. Horses who raced at age two posted 44 wins and 128 top-three finishes from 718 starts, meaning 6.1% of them won and 17.8% finished in the top three. Based on these percentages, Apollo Curse qualifiers were 56% less likely to win the Kentucky Derby than the starters who did race as juveniles, and they were 25% less likely to finish in the top three.

Before moving on, there’s another question that’s worth analyzing: do horses without juvenile racing experience outperform their post-time odds? If bettors have historically viewed Apollo Curse qualifiers with skepticism (which is warranted based on the data we outlined above), then there’s a chance these horses are chronic overlays in the betting. Even if they’re less likely to factor than horses who raced at age two, perhaps the Apollo Curse qualifiers consistently outperform their odds.

To determine if this is the case, we’ve reviewed every Apollo Curse qualifier since 2001, the year Churchill Downs started offering individual odds on every horse in the Kentucky Derby field. We’ve identified the ranking of each Apollo Curse qualifier in the betting (first choice, second choice, fifth choice, 12th choice, etc.) and compared their ranking to their actual finishing position:

The numbers aren’t encouraging. On average, horses without juvenile racing experience started as roughly the eighth choice in the betting, but their average finishing position was about 10th, indicating they ran below the expectation of bettors. Indeed, only 37% of Apollo Curse qualifiers matched or exceeded the expectation of bettors, while 63% performed worse than expected.

Conclusions

The Kentucky Derby is not a static race. Each year brings a new field of contenders, and there’s a chance the recent victories by Justify and Mage are signaling the start of a new era in which horses without juvenile racing experience are no longer at a disadvantage.

But even with the victories of Justify and Mage, the broader history of the Kentucky Derby since 1937 indicates that when horses without juvenile experience enter the Kentucky Derby starting gate, they’re 56% less likely to win than horses who did race at age two, and 25% less likely to finish in the top three.

Furthermore, even if the next three or so Apollo Curse qualifiers win the Kentucky Derby, they’ll only reach equal footing with the success rates of horses who did race at age two.

The conclusion is straightforward: for the foreseeable future, the Apollo Curse lives on, and horses who did not race at age two are at a meaningful statistical disadvantage in the Kentucky Derby.