Maple Leafs forward Joffrey Lupul, who was suspended two games this week for a hit on Victor Hedman, tweeted in response, "If someone can explain the decisions on what warrants a suspension and what doesn't, please let me and the rest of guys know."
Brendan Shanahan and the NHL's Department of Player Safety informed the Rangers and Panthers of the news on Friday afternoon.
Late in the third period of the Rangers' 3-1 loss to the Panthers, Nash came at Kopecky as he took a shot from between the circles. Nash left his feet and apparently elbowed Kopecky in the back of his head. The Panthers forward, who wasn't facing Nash, was down on the ice without his helmet for a few seconds before skating off.
Nash wasn't called for a penalty, while Kopecky was able to return to action and scored an empty-net goal later in the period.
Later on Friday evening, the NHL released a video explanation of why Nash was not suspended.
The explanation made three key observations of Nash's hit, noting that Kopecky turned prior to moment of contact, his head was not targeted, and his head was not the principal point of contact.
"Although we do not think this was a legal hit, we also believe it does not rise to the level of supplemental discipline," said the league in the video.