I'll tell a quick story about rider selection.
Out of nowhere a guy gives my trainer ( 4 horse barn) an horse who had never raced before. For our barn getting a new owner etc was a big deal. The owner talked this horse up to no end. This horse had so much ability, the half-brothers and sisters were so good blah blah blah. The owner insisted on running the horse long on the grass for his debut. It was quickly apparent this horse had no ability and belonged in MCL 7500 or lower going short but you do what the owner wants.
For his debut we got Don Brumfield to ride for the sole purpose that he wouldn't BS you. A lot of riders tell you this or that after a race so they can ride the horse back, Brumfield tells you what he thinks like it or not.
The horse ran 6th in his debut, Brumfield came back to unsaddle got off the horse and said to my trainer " I hope you're not paying the bills on this one"
Later my trainer told the owner what he thought of the horse and what Brumfield said about the horse. The guy took his horse and gave him to another trainer. The horse never did break his maiden. not an exciting story but a story nonetheless.