Canada's Felix Auger-Aliassime looks on during his match against Serbia's Dusan Lajovic at the men's National Bank Open tennis tournament in Toronto, Wednesday, Aug. 11, 2021. (Christopher Katsarov/The Canadian Press via AP)

Canada's Felix Auger-Aliassime returns the ball to Serbia's Dusan Lajovic at the men's National Bank Open tennis tournament in Toronto, Wednesday, Aug. 11, 2021. (Christopher Katsarov/The Canadian Press via AP)

Serbia's Dusan Lajovic, left, shakes hands with Canada's Felix Auger-Aliassime after Lajovic defeated Auger-Aliassime at the men's National Bank Open tennis tournament in Toronto, Wednesday, Aug. 11, 2021. (Christopher Katsarov/The Canadian Press via AP)

Serbia's Dusan Lajovic reacts after defeating Canada's Felix Auger-Aliassime at the men's National Bank Open tennis tournament in Toronto, Wednesday, Aug. 11, 2021. (Christopher Katsarov/The Canadian Press via AP)