Tua comes off as an intelligent guy - after 3 concussions (that we know of), I would hope he would speak to those who have been down this road in the NFL and other sports to see what life after football might hold. No amount of $ is worth permanent damage to the brain and I'm sure he knows that. It's the competitor in him that will wake up one day, feel pretty good, and want to get back at it and the docs just might let him. Then #4 comes and maybe #5 ...
Hang it up Tua while you can - don't end like Kuechly, Chris Pronger or worse, Steve Montador.