The adage is that racing is twenty per cent jockey and eighty per cent horse. If a horse wins by five lengths or more, it was the horse; the jockey only had to avoid mistakes, such as getting pinned on the rail or taking a turn too wide. But in close races the jockey’s tactics and riding skills can be decisive.
–John Seabrook “Puerto Rico’s Ortiz Brothers Light Up Horse Racing” The New Yorker