Toronto FC striker Jozy Altidore suffered a hamstring injury in Toronto FC's 4-3 defeat to the Vancouver Whitecaps on Saturday night.
Vancouver was already ahead 2-0 when Altidore had a penalty attempt saved and immediately exited the game.
Altidore will now be in a race to be fit before the United States begin play in the Copa America on June 3. Final squads for the tournament must be submitted by May 20.
After Kekuta Manneh and Christian Bolanos scored inside the first 18 minutes, Sebastian Giovinco then scored twice to pull Toronto even, moving into sole possession of the franchise record for career MLS goals with his 29th and 30th strikes.