Forward Devante Smith-Pelly broke his left foot after blocking a shot in the second period of Canada's 8-1 rout of Finland on Monday and will miss the remainder of the tournament.
"Heartbreaking way to end my tournament, but I know the guys will do the country proud regardless. Thank you everyone for your kind words," said Smith-Pelly on his Twitter page.
The Anaheim Ducks forward, one of only two NHL players on the Canadian team, cannot be replaced on the 22-man roster.
The only situation in which a team could add another player at this point in the tournament would be in the case of a goaltender injury.
The six-foot, 207-pound Toronto native scored twice Thursday in Canada's 7-1 pre-tournament win over Switzerland 7-1.
The Ducks drafted Smith-Pelly in the second round, 42nd overall, and has contributed three goals and two assists in 26 games with Anaheim this season.
"This is a very unfortunate injury for Devante," said Ducks general manager Bob Murray in a statement. "We anticipated him playing a prominent role for Canada at the 2012 world junior tournament. Although this is a big loss for Canada and the Anaheim Ducks, we fully expect Devante to return to full health this season."
Hockey Canada says Smith-Pelly will remain with the Canadian junior team.