Canada’s Gabriel Diallo dropped a 6-2, 2-1 decision to Hugo Gaston of France in qualifying play on Sunday at the National Bank Open.
The match ended after 58 minutes when the 20-year-old Montrealer was forced to retire due to heat exhaustion.
Diallo, a wild-card entry who plays for the University of Kentucky, was the lone Canadian to reach the second round of the 28-man qualifying draw.
Play was suspended due to rain later Sunday with two matches yet to be completed.
With the win, Gaston earned one of seven qualifier berths in the 56-player main draw starting Monday at IGA Stadium.
Fabio Fognini of Italy also advanced with a 6-3, 4-6, 6-2 victory over Germany’s Daniel Altmaier and Benoit Paire of France beat Marc-Andrea Huesler of Switzerland 6-3, 3-6, 6-1.
Arthur Rinderknech of France defeated Japan’s Taro Daniel 6-4, 6-4 and Britain’s Jack Draper beat Quentin Halys 3-1 after the Frenchman retired.
Montreal’s Felix Auger-Aliassime is the only seeded Canadian player at No. 6. Denis Shapovalov of Richmond Hill, Ont., is also in the main draw along with wild-card entries Vasek Pospisil of Vernon, B.C., and Alexis Galarneau of Laval, Que.
Defending champion Daniil Medvedev of Russia is the top seed at the US$6.57-million ATP Tour event, which runs through Aug. 14.