Well Chavez has sparred GGG and he has an idea what to expect. He also noted that Golovkin got tagged by some big shots by Brook, and maybe feels he has slipped.
I always wanted to see that fight back when it was being talked about. He probably couldn't beat GGG but he would have gone the full 12.
I don't think Chavez could've ever beaten Golovkin, but when he was still able to make 160, I can see him being one of the only guys that could go the distance with Golovkin.