First of all, I wanna start saying that IM Andersons fan and I "like" GSP (or at least dont have anything against him).
However, sometimes we are BLIND fans and we start to ignore reality !!
I think their retirement speech (search GSPs mentor saying GSP should retire sat night thread) has more than simply age, legacy and "done" with the sport. It might have a touch of fear as well.
My point is that in MY opinion, Anderson and GSP got in into a situation right now where they know that the competition will only get harder and harder with new upcomers, new breed of fighters and hard to keep up ! Fighters who truly know how to beat them (refer to Weidman for instance).
Anderson ALREADY tasted some of this reality by being KTFO doing the exactly same thing he did for years with other fighters he fought before Weidman (not to mention Weidman didnt deserve that title shot lmao). Even if Anderson beats Weidman in december, he still got Vitor, whos coming hungry, maybe Mousasi and may have to fight Machida and Jacare (I doubt he would anyways) which could be bad matchups for Anderson. Bottom line: Cote, Maia, Leites, Bonnar and Griffin were "good old days for Andy" and his legacy.
Same thing is coming on GSPs path right now.
Hes facing a guy who I dont think will beat him BUT will definitely expose more of his game. After that, he might be forced to fight Rory, he might be facing dudes like Lawler (if he beats Rory), Brown, Condit 2, even Maia PLUS all these guys who are coming for gold. Not an easy task for GSP anymore. No more one dimensional fighters like Hardy and Alves and maybe not as many fights in Canada either. Not to mention that if he beats Hendricks and Anderson beats Weidman, GSP might be "forced" to fight Anderson which we all know he DOES NOT want to do it !
Have a good one folks
ps. Of course they are not scared of anyone ! Just a way to say !