No details on Gronkowski's situation have emerged, but it's possible that he simply felt the early signs of a muscle cramp. Temperatures reached the 90s Monday, and Gronk has many muscles to cramp.
In all likelihood, Gronk will sit in the preseason, as will Julian Edelman.
The story was mostly about just how cautious can the Pats be with Gronk. After a healthy 2016, hopefully for owners this was just a cramping situation. At some point, Gronk and Edelman will have to get back out there.