I have never seen anybody knock out Mayorga in the 12th round. Oh wait an old Shane Mosley did it. And past prime versions of Trinidad and DLH both knocked out younger and fresher Mayorga in under 6 rounds.
Not that Cotto is past prime...just that he was never that good to begin with. And he certainly isn't even what he used to be back then, which was not a big deal anyways.