Zverev, the German star coming off a victory last week in Washington, double-faulted on match point to send Tsitsipas to his first ATP World Tour Masters 1000 semifinal.
Tsitsipas reached his first ATP World Tour final earlier this year at a clay-court event Barcelona, losing to Spanish great Rafael Nadal in the championship match.
Defending Rogers Cup champion Alexander Zverev of Germany blew past Russian qualifier Daniil Medvedev 6-3, 6-2 to reach the quarter-finals. 'I do remember when I played Djokovic, I was able to get to the point, and I was able to construct points the way I wanted to.
Jorginho scores penalty as Chelsea win and Crystal Palace spoil Fulham's return
Discussing his arrivals, the manager said: "The club was willing and we took a great goalkeeper, very young but he can become a great goalkeeper".
This time past year, Greek teenager Stefanos Tsitsipas had yet to record a victory on the ATP World Tour.
Bulgarian fifth seed Grigor Dimitrov laboured for nearly two and a half hours to subdue Frances Tiafoe of the United States 7-6 (7/1), 3-6, 7-6 (7/4).
"The early break in the third set was everything".
"I thought Tsitsipas played very well and he deserved to win without a doubt", Djokovic said.
Hundreds evacuated from campsites as southern France hit by flash flooding
The French weather service has issued orange and yellow alerts for parts of southeast France that will remain in place until 4pm. Ten people were taken to hospital suffering from hypothermia and minor injuries, said regional police spokesman Jerome Tallaron.
Heavy morning rain pushed back the opening matches at the York University campus in the north end of the city by about an hour, holding off the start of an exciting day that featured six Canadian players, including Montreal's Felix Auger-Aliassime on his 18th birthday. But I think one is good to give away to a top player, but two is, in my opinion, pushing it'.
He next faces Wimbledon runner-up and fourth seed Kevin Anderson who defeated Ilya Ivashka of Belarus 7-5, 6-3 to also make the last-eight. Maybe if I played Chung it could be a little bit just having the home crowd support.
Milos Raonic of Thornhill, Ont., was scheduled to follow Djokovic's win on centre court but that match was also delayed.
Garcia proved too strong for Sharapova with a 6-3, 6-2 win and will take on top seed Simona Halep of Romania in the quarter-finals of the Women's Tennis Association Premier 5 tournament.
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The ref needs to explain that to us because I don't understand why (it was not retaken)". We all know Thibault's quality, but Thibault's not a Chelsea player anymore.
Denis Shapovalov of Richmond Hill, Ont., - the only Canadian player remaining in the tournament - was to face Robin Haase of the Netherlands on Thursday evening.