Rothstein has another entry in WolverineNation's exit interviews, this time talking to Nate Brink.
The article is paywalled, but it talks about how and why his career ended. Apparently he had several concussions, and the last one was severe enough to hospitalize him and end his career.
Sad story to read, but it sounds like he's happy he was able to make the right decision:


Hoping he isn't impacted over the long term like the stories you're beginning to see.