After running back Dion Lewis gained five yards on a run, McCain hit Danny Amendola in the head. That was enough to earn an unnecessary roughness penalty and an ejection.
As Charean Williams of Yahoo Sports noted, "Amendola grabbed McCain's jersey and pulled him to the ground on top of him."
James Walker of ESPN.com provided more details:
The Dolphins were trailing 21-10 at the time, and the Patriots scored a touchdown two plays later to go up 28-10 early in the third quarter.
As ESPN.com's Kevin Seifert noted, McCain was the 10th player in the league to be ejected this season.
The 24-year-old has appeared in all 11 games for the Dolphins this season and hasn't missed a contest since entering the league in 2015. In that time, he has developed into a valuable coverage player, especially in sub-packages.