Two of a kind???

What do these two guys have in common?

Both have a name that starts with B
Both were great athletes and are real fast for their size
One won a leg of the Triple Crown the other one came close to winning the Triple Crown
Both are mostly dark brown in color
Both have suffered major leg injuries
Both have about the same size head
One has a few tight screws in his leg... the other has a few loose screws in his head
One will be taking horse steroids to help him heal from his shattered leg the other guy has already been there... done that
One is hung... ehhh... like a horse, the other one? Not so much (I hear steroid shrinks the package)