Wow.....I have to say I am confused as to why some would answer porcupine, or anything other than deer for that matter.
It is clearly a buck rub and fairly recent to boot.
What seems odd though is that is the only visible rub on the road.
Blacktails often travel the roads during the rut and will rub/hook/horn every so often but they don't always make a rub line like whitetails.