Northern Dancer.
I googled \"Northern Dancer hoof problems\" and one of the results is a Google Books preview of a bio of EP Taylor. The book says ND had a quarter crack prior to the Remsen (as a 2yo, obvs), but still ran in and won the Remsen (with the crack still present !!!). After the Remsen, they found a vet who had a new way of \"patching\" cracks (so that you didn\'t have to turn them out for months on end and let it heal naturally). They patched him, and, within a month or so, he started that string of graded victories Richiebee listed, culminating in the Derby victory. He also won the Preakness, but was denied the Triple Crown by Quadrangle.