Dr. Robert Cantu, of the Cantu Concussion Center, is a concussion expert who helped write the NFL concussion protocol and he says of those with a concussion, “the majority will recover in within usually two weeks. That’s why, most probably, Gronk will be back for the Super Bowl“

https://www.nbcboston.com/news/local/Will-Gronk-Clear-Concussion-Protocol-and-Play-in-the-Super-Bowl-470591673.html