I think it's a lot more than his groin. From the start of the season it was pretty clear to me that he's lost his burst. When you're Branch's size and strength, your entire game hinges upon your ability to separate on one step. I could see that he no longer could get away from corners, and while he has an impressive repertoire of moves those too hinge on his burst. Guys are getting their hands on him too easily, and breaking with him too easily. This is further backed up by how he only makes play on scramble drills. On scramble drills it's not about your ability to separate so much as it is your ability to find an open area. He's effective there while ineffective everywhere else. That's evidence of tires that have run out of tread.
Not fun to hear, I know, but when guys like him lose their burst it's a pretty abrupt halt.