Boston Bruins forward Shawn Thornton filed an appeal Monday of the 15-game suspension he received from the NHL.
The NHL Players' Association announced Thornton's appeal on Twitter.
NHL commissioner Gary Bettman will conduct a hearing on the appeal. Should Bettman rule against Thornton, the player could take the case to an outside arbitrator.
Thornton's suspension was the longest issued in the regular season by NHL senior vice president Brendan Shanahan in his two years on the job.
The punishment is a response to an incident involving Thornton and Pittsburgh Penguins defenseman Brooks Orpik on Dec. 7. Thornton grabbed Orpik from behind at the 11:06 mark of the first period and punched him in the head two times.
Orpik left the game on a stretcher with a concussion and was taken to a hospital. He is skating again but has yet to return to action.
Shanahan ruled that Thornton's action were an "act of retribution" after Orpik hit Bruins right winger Loui Eriksson earlier in the game.
Thornton, who will forfeit $84,615.45 in salary if the suspension is upheld, never was suspended previously in his 11-year NHL career.
Thornton, 36, has three goals and no assists in 27 games this season, his seventh with the Bruins. He previously played for the Chicago Blackhawks and the Anaheim Ducks.