Since everyone one likes to talk about this $hit...

You should understand the western boxer's guard and defense (and train it).
You should understand the need for basic strength training and conditioning (and train it).
You should understand the fundamentals of the basic ground game (and train it).

Do you, as a TCMAist, need to know anymore than what's posted above? No - not really. Those three things if trained properly will increase your understanding of the sporting combative arts and you'll gain some good knowledge that you can use in self defense... after that you got all that you need from the sporting world and you're free to get back with your training. Enough of this MMA crap already.