The Australian will start fourth for the race behind George Russell, Max Verstappen, and team-mate Lando Norris following a “messy” qualifying session.
Held in dry conditions, teams spent much of it covering off the threat of rain which ultimately saw Russell’s pole lap slower than the time he set in Qualifying 2.
And while Mercedes has looked fast throughout practice, so too has McLaren, while the Red Bull has looked more difficult to drive.
“It was a bit of a messy session all round I think, for everyone,” Piastri said after qualifying.
“It was very tricky. Look at George, he went three-tenths slower from Q2 to Q3 and he’s on pole.
“With the rain and with the wind as well, it just makes life so tough. I think there’s a lot of people out there that can say they could have found three- or four-tenths out there.
“If you did a perfect lap, you honestly could have been on pole by nearly half a second, probably.”
While admitting there was potentially more to be had in qualifying, Piastri remains optimistic that he can push forward in the race.
“I’ve kind of learned, especially with some of the races this year, to not predict how we’re going to go,” he joked.
“Now that we’re really at the front, [we can] aim for a win every time.
“Of course, we’re not going to win every race, but I don’t think we shouldn’t be trying to aim for any less than that.
“We’ve had a quick car this weekend and, in a session like that where it’s so easy to get it wrong, I think having both cars on the second row is a really good result for the team.
“These are the kind of days where it can really spiral for you,” he added.
“For me, personally, and for the whole team, it’s just a good solid result.”
Rain is forecast for tomorrow’s grand prix, with that chance rising ahead of race start time at 14:00 local time (04:00 AEST).
The Circuit Gilles Villeneuve has been resurfaced since last year and is less abrasive than it was, resulting in less grip.
With Friday’s running held in changeable conditions, and rain washing the circuit following Free Practice 3, it remains green.
“It’s definitely different to last year with the resurfacing,” Piastri noted.
“It kind of just feels like it’s not had that much use, so it’s really kind of been rubbering up through the day.
“Very difficult to get the tyres warmed up. It’s very smooth, it’s almost like Las Vegas in some ways where you never really know whether it’s just one timed lap is going to be the best.
“In the dry we’ve looked competitive. I think in the wet we’ve looked competitive,” he added looking to his chances in the race.
“Nobody really knows what the tyre is going to do in either situation – I think the longest run anyone’s done is like six or seven laps.
“I don’t really mind either way.
“It would potentially be a bit of a better race if it’s dry, a bit more strategy involved, a bit easier to overtake possibly.
“But if it’s wet, there’s a big change for people to make mistakes, so I’m sure it’ll be exciting either way.”