Rafael Nadal, Novak Djokovic and Alexander Zverev headline the Rogers Cup in Toronto. "I'll take it as a good experience and look forward to the next event".
He was replaced by the 27-year-old Bosnian who was outclassed early, but troubled the 4-time Canadian champ in the second, breaking him twice late, before falling.
Nadal will next face Marton Fucsovics of Hungary or Swiss Stan Wawrinka.
"And I'm all in favour of that", Djokovic said after beating Peter Polansky, 6-4, 6-3 to reach the third round of the ATP Toronto Masters on Wednesday. The German beat the Greek in the only previous meeting at last week's Citi Open, but Tsitsipas is very confident as he is coming from the upset over Novak Djokovic.
Heavy morning rain delayed the match 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 five matches with Canadian players, including Montreal's Felix Auger-Aliassime on his 18th birthday. "I'm trying to get some confidence from winning matches".
Meanwhile, third seed Juan Martin del Potro was forced to withdraw prior to his opening match due to a left wrist injury.
German second seed Alexander Zverev, the victor last week in Washington, beat American Bradley Klahn 6-4 6-4 while fourth-seeded South African Kevin Anderson edged Russia's Evgeny Donskoy 4-6 6-2 7-6 (7-0).
"Sorry to my fans in Toronto, but I have to pull out of the tournament since my left wrist needs some days of rest", del Potro said in a tweet.
There was some joy for Canada after emerging star Denis Shapovalov beat 14th seed Fognini 6-3 7-5.
Play was also suspended in the match between world number one Simona Halep of Romania and Russia's Anastasia Pavlyuchenkova.
Rain interrupted the first set at 6-5, but the Spaniard immediately broke when play resumed to take the set. So now I'm going to use it in my favor for my next match against him and try to get the most out of it.
"(I need) the consistency of playing on a high level match after match, I haven't had that postsurgery for several months", Djokovic said.
Maria Sharapova continued her bid to climb back to the top of women's tennis with a 6-0, 6-2 victory over 12th-seeded Daria Kasatkina.
Nadal said. "I follow the rules". So I'm not the type of player to really, the type of guy, in general, to get excited for wins.
The Russian will face sixth-seeded Caroline Garcia of France in the third round. Garcia came from behind to defeat Magdalena Rybarikova in three sets 4-6, 6-1, 6-3 on Tuesday.