Canada Soccer said the Inter Milan player sustained the injury during Tuesday's session in Fort Worth, Texas.Â
Training was cancelled after Buchanan was taken away in an ambulance.
The 25-year-old had featured in all three of Canada's group-stage games at the Copa America as they reached the knockout stages in their tournament debut.
"He has been taken to a local hospital for further evaluation and treatment," the Canadian men's national team said in a statement, later confirming the player would have surgery to repair a broken tibia.
According to sports network TSN, who spoke to Canada defender Alistair Johnston, the injury to Buchanan occurred after a "coming together" of players during a drill.
Johnston told TSN the injury could be heard as soon as it happened and went on to describe the team's mood as "sombre".
Buchanan signed with Inter from Belgium's Club Brugge in January, becoming the first Canadian to play in Italy's Serie A.
Canada finished second behind Argentina in Group A at the Copa America with a 1-1-1 record and are scheduled to face Venezuela on Friday in Arlington, Texas.
- with Reuters
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