Vancouver's Scott Tupper scored in the 55th minute as Canada dropped its second straight game of the Olympic field hockey tournament, 3-1 to Argentina.
Gonzalo Peillat scored twice and Matias Paredes added one to lift Argentina to 1-1-0. They opened the tournament by tying the Dutch.
Tupper's goal came off a penalty corner.
Canada slipped to 0-2 after a 6-2 opening loss to Germany.
The Canadians will have another tough task Tuesday when they face the Netherlands, 5-0 winners over Ireland on Sunday.
Canada will be hard-pressed to advance to the quarter-finals as only the top four from each of the two pools go through.
After missing the London Olympics four years ago, Canada qualified for the Rio Games with a fourth-place finish at the International Hockey Federation's World League semifinal in Argentina last June.
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