McDonagh, who was playing in only his second game after missing four games because of a concussion, returned to the Rangers bench and was attended to by trainers but did not return for the start of the second period. The team announced he would sit out the rest of the game as a precaution.
The NHL announced it will hold a hearing with Komarov on Friday.
Rangers coach Alain Vigneault said after the game that he did not have an update on McDonagh's condition. Asked about the hit, Vigneault said, "I'm not going to comment on that. I'm going to leave it to the league and the referees to do their jobs."
The match penalty, which indicates an intent to injure, means Komarov was ejected from the game and is subject to suspension pending review by the league. Komarov leads the Leafs in points (35) and goals (18).
ESPN's Pierre LeBrun and Craig Custance contributed to this report.