Recently there have be estimates given in this forum that a horse's chance of winnning breaks down to 96% horse, 2% jockey, and 2% whatever. I feel these numbers grossly underestimate the importance of the jockey. There are others who feel the same way.
For example, take this conversation from the movie The Big Sleep. Always cautious private eye Phillip Marlowe, played by Humphrey Bogart, is getting to know Vivian, a wealthy, heavy drinking gambler, played by Lauren Bacall:
Phillip Marlowe: "Well, I can't tell till I've seen you over a distance of ground. You've got a touch of class, but I don't know how, how far you can go."
Vivian: "A lot depends on who's in the saddle."
That's all I have to see. Vivian says that who you put in the saddle is important. Vivian knows.
We can argue over what Vivian means by "a lot," but you better believe it's a lot more than 2%.