Carlson, who has a history of concussions dating to his career in Seattle, missed the Vikings' game Thursday night. His health is obviously the most important factor relating to the play.
The play also produced a $21,000 league fine against Johnson for an illegal blindside hit. Officials levied a 15-yard penalty against Johnson and the Cardinals.
Carlson seemed to see Johnson approaching. He even lowered his shoulder as if to brace for impact. But when Johnson delivered a helmet-to-helmet blow on the play, an official threw a flag. The helmet-to-helmet aspect of the play was what referee Terry McAulay emphasized when announcing the penalty as a personal foul for unnecessary roughness.
"Illegal blindside block" was the penalty as listed in the NFL gamebook, and that was the notation when the league fined Johnson, according to various reports.
One of the NFL definitions for a defenseless player is one who "receivers a blindside block when the blocker is moving toward or parallel to his own end line and approaches the opponent from behind or from the side."
Whether Carlson saw Johnson coming doesn't seem to be pivotal to the ruling or the fine. Carlson was moving parallel to his own end line. Johnson approached from the side and and struck him. Johnson made helmet-to-helmet contact, too.
That's a penalty and a fine, according to the league.