Reverse Nerd

Someone who used to be a jock and non committed to studying or preparing commitments in advance, but has now become nerd at a later stage in life.

Possible opposite: A person that always was a goody-two shoes but then became unravelled.

Jill was always such a procrastinator and never read up on the course material, but now she has become a Reverse Nerd even enjoys studying in her free time. .