Thornton's agent, Anton Thun, confirmed in an email that his client was appealing. The NHL Players' Association announced it had informed the league of that plan before the 48-hour deadline to do so passed.
As laid out in the collective bargaining agreement, the appeal first goes to commissioner Gary Bettman. If Bettman upholds the suspension, Thornton and the NHLPA can then elect to appeal to a neutral arbitrator because it is for six or more games.
Buffalo Sabres forward Patrick Kaleta is the only player to use this appeals process under the new CBA, and no player has gone to the neutral arbitrator. Bettman upheld Kaleta's 10-game suspension for an illegal hit on Columbus Blue Jackets defenceman Jack Johnson, issuing a 17-page decision.
Thornton got 15 games for slew-footing Orpik to the ice and landing gloved punches to his head during a game Dec. 7. The Pittsburgh defenceman was knocked unconscious and has not played since because of a concussion.
Vice-president of player safety Brendan Shanahan said it was not a spontaneous action by Thornton because he tried to confront Orpik earlier after Orpik injured Bruins winger Loui Eriksson with a hit.
Appearing on TSN Drive with Dave Naylor on TSN 1050, Thun said he could not talk about the case before it was presented in the appeal hearing but did mention he felt there was more than one reason for Thornton to appeal his suspension.
"We believe there are a variety of reasons to appeal it and part of it is just clarity… The clarity is not just Shawn but for the other players in the league."
Thun was also asked if he was aware of when the appeal hearing will take place with Bettman.
"To be the best of my knowledge the meeting will be later this week, Thursday and Friday have been thrown around but at this point in time it hasn't been confirmed."
Thornton had not been fined or suspended before. Several general managers and coaches around the NHL have spoken in support of Thornton's character in his career before this incident.
The Oshawa, Ont., native apologized for his actions after the game.