McMillian did not lead with his helmet but appeared to use his shoulder to hit Scheffler in the head during the fourth quarter of Sunday's game at Lambeau Field.
The league said McMillian was fined for "striking a defenseless receiver in the head area with his shoulder."
Scheffler has not practiced all week because of a concussion.
ESPN.com Lions reporter Michael Rothstein reported that Detroit defensive tackle Ndamukong Suh was not fined for tripping Packers quarterback Aaron Rodgers in the first quarter of Sunday's game. Suh was penalized on the play.