The usual guesstimates are that a jockey accounts for 10 percent or "just a little bit" of a horse's performance, and that a jockey's influence is as likely to be negative as helpful. "A great jockey cannot make a slow horse win," Hall of Famer Jerry Bailey has said. "But a bad jockey can get a great horse beat."
If a jockey understands the track that his horse is running on, and if he develops a good strategy based on the competition he's facing, he'll have a smooth run. If he doesn't, his horse will look terrible. That's a recipe for all of us to recognize downside more easily than upside.