Piastri finished fourth in Montreal, two hundredths behind teammate Lando Norris, as George Russell led a Mercedes front-row lockout ahead of championship leader Kimi Antonelli.
While McLaren had reduced the gap to the Brackley squad with upgrades introduced in Miami last round, Piastri said Mercedes remained the team to beat after another commanding display in Canada, where the championship leaders also brought their own updates to the Circuit Gilles Villeneuve.
“I mean it was feeling pretty good,” Piastri told Sky Sports.
“A bit of a messy day for everybody I think. But the Mercedes still looks very strong.
“So I think that’s probably the biggest takeaway from today unfortunately. But we’ll see what we can do.
“See how we can optimise things a bit better and try our best again tomorrow.”
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Russell secured sprint pole with a 1m12.965s, finishing 0.068s clear of Antonelli, while Norris and Piastri completed the top four ahead of the Ferraris of Lewis Hamilton and Charles Leclerc.
Despite McLaren again falling short of Mercedes over one lap, Piastri believed the team could still capitalise on its strong starts in Saturday’s sprint, particularly in fending off the Ferraris behind.
“I mean our starts have been better than the Ferrari’s all year, so we’re confident in ours,” he said.
“I’m sure it’s only a matter of time before Mercedes get theirs competitive as well.
“But until that time comes, we’ll try our best to take advantage of it.”
McLaren team principal Andrea Stella explained the squad had opted against running a revised front wing package during sprint qualifying as it continued evaluating the update.
“I think it’s a fair margin considering that they had important upgrades here,” Stella said. “We also had some upgrades.
“We actually wanted to take a bit more time to see the behaviour of the front wings, so we race with the previous front wings.
“So looking at the fact that the car is pretty much the Miami car, it’s a gap that remains encouraging.”
Stella said the sprint format influenced McLaren’s decision to stick with a more familiar setup package.
“When it’s a sprint event, you know that you only have one [practice] session,” he said.
“We want to race a car that we know. We want to race a car that is predictable.
“So for the moment we are going for the Miami front wing.”
The Canadian sprint take place at 2am AEST Sunday (12pm local time Saturday).
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