Greig (upper body) sustained an injury in Team Canada's game versus Switzerland at the World Junior Championship on Wednesday, per TSN.
The exact nature of his injury wasn't reported, but it appeared Greig was favoring his shoulder. Team Canada didn't provide an update after the game, so he should be considered day-to-day ahead of the rest of the tournament. If the injury is significant, Greig could be in doubt for the Senators' training camp.