I know that Borel is the master at Churchill. When not in KY, where does he usually ride and is he as good at those tracks? How about tracks that are out of his usual circuit -- and has he really had that much experience out of his comfort zone?
It sounds like MTB is going to need a jockey who has a good clock in his head, can figure out how to run at Mountaineer, Saratoga and Santa Anita, and can keep/put the horse in the right spot until it's time to make that run to the wire. From reading comments by Woolley, it also sounds like MTB's rider needs to have a decent amount of moxy to find those spots.
So, who might fit that description?