I have seen some people try and argue that refusing the treatment that the team doctor puts forth is a action that would rise to the level of failing to meet the requirements of the SPC. Just like if a player has any other injury and refuses to work with the athletic trainer to get treatment, etc.
It is a rare scenario and I am sure that if the Sabres tried to go that route that there would be a battle between the NHL and NHLPA.
I think part of it comes from the SPC clauses 2(a) and 2(b)
The Player agrees to give his services and to play hockey in all NHL Games, All Star Games, International Hockey Games and Exhibition Games to the best of his ability
under the direction and control of the Club in accordance with the provisions hereof. The Player further agrees,\
(a) to report to his Club's Training Camp at the time and place fixed by the Club, in good physical condition,
(b) to keep himself in good physical condition at all times during the season,
There might be other parts too in the health section, I'll have to double check. I don't doubt that the Sabres can try suspending him and may indeed have a very decent case to do so. But I also don't doubt that the NHLPA will get involved and probably Bettman too. There was a case a few years ago of this happening with an NHL player but I'm drawing a blank on who it was and the full details.