On this Wednesday before the 2015 Kentucky Derby, here’s my secret tip on how to pick a horse who can successfully negotiate 10 furlongs for the first time in his life. Yes, speed is important. And equally important is the breeding to go a distance. Race record is most important of all, especially the proven ability to run a final quarter faster than the other quarters of the race.

But here’s something that experts never talk about. The Kentucky Derby is almost always won by a horse whose dam was a good racehorse. In fact, the racing quality of the dam may be the most significant factor in picking a horse to run well in the Derby. Notice I don’t say “win.” Just “run well.” In a 20 horse field the most you can realistically hope to choose is a horse who will perform well.

With the glaring exception of California Chrome last year, almost every winner in modern history has been a horse whose dam has performed well herself on the racetrack. Looking at the history of the race you’ll find an occasional winner with an unraced dam or one whose dam had a brief (but usually promising) career. In general, the racing quality of the dam plays a surprisingly significant role in the success of the horse the first time he’s asked to run a distance.

It could be coincidence, but there equally could be a real reason for it. Winning at any distance, but particularly the longer ones, requires toughness and determination, not just speed. A good racing mare might be expected to pass that on to her offspring.

So what does that mean for this year? Unfortunately the likely favorite American Pharoah is out of a mare who failed on the racetrack. Upstart’s dam was unraced. Mubtaahij’s dam failed to win in nine starts.

Among the top choices, Frosted is out of Fast Cookie, the winner of more than 500 thousand. Firing Line is out of the good stakes winner Little Girl Blues. Materiality is from a stakes winner named Wildwood Flower. Dortmund is out of a stakes winner named Our Josephina.

But remember this: a great horse can rise above anything. Secretariat’s dam never won. American Pharoah, if he truly is great, can rise above his mother’s racing record.