Maybe im proven wrong in the next day or two, but I think I know what happened. It wasn't an injury. He "cricked" his neck, which causes an intense pain, but only for a few moments. It goes away about a minute later and you're fine. This happens to me sometimes and explains why Kermit was ready to fight afterwards.
Was really looking forward to this fight and hoping Kermit would acquit himself. Oh well.. now I can focus on the other undercard.