The collision took place late in the second period of Ottawa's 4-2 win over Montreal Thursday in the opener of their Eastern Conference quarterfinal playoff series.
Eller was the victim of a blindside hit that left him bleeding and unconscious. He reportedly suffered a broken nose and lost several teeth.
He was hospitalized overnight Thursday and released early Friday. He was not available for action when Game 2 was played Friday.
NHL director of player safety Brendan Shanahan said a study of the video replay showed "Gryba makes Eller's head the principal point of contact, causing a serious injury."
"In attempting this very difficult check," Shanahan said, "Gryba does not hit squarely enough through the body. A hockey player bears some responsibility to be aware of an impending check, however, since the inception of the current 'illegal check to the head penalty,' no player should expect that his head will be made the principal point of contact, whether intentionally or recklessly."
Gryba received a game misconduct penalty.
Notable deaths of 2014 [PHOTOS]