Ferrari brought a revised floor and front wing to this weekend's Red Bull Ring sprint event as part of its strategy to fast-track plenty of smaller upgrades.
The revised package appeared to give Leclerc and Sainz an immediate boost after just a single free practice session to dial them in on Friday, as the pair qualified in the top three behind Red Bull's polesitter Max Verstappen.
"I don't think we expected to be so close to the Red Bulls, so it's a good step forward," said Leclerc after conceding just 0.048s to the Dutchman.
"First of all, I would like to thank all the guys back at the factory. It's only qualifying but the work they've done in the last two, three weeks in order to bring the package earlier than what it was planned was really, really impressive. And that helped us to have a good performance today.
"It feels good to finally have a clean qualifying again and to be back on the front row, the feeling has been a bit better in the last few races.
"I've managed to put everything that I wanted in the last lap of Q3, very close to Max but not enough today."
But while Ferrari has looked impressive on one-lap pace in 2023, it has struggled with race pace consistency and tyre wear on higher downforce circuits.
Therefore, the jury is still out on whether Leclerc and Sainz can stay up front or whether their race pace issues strike again at a track that punishes the tyres much more than the previous Canadian Grand Prix.
"Race pace looked quite good in Montreal, but again, consistency is where we need to focus," Leclerc acknowledged.
"So, we really have to see on Sunday if we've got the same pace as Montreal, but Red Bull for now is quicker on race day, so it's going to be difficult.
"But if we can put them in difficulty, we'll do it."
Sainz added that Ferrari ended up "closer to Max also maybe than expected" as the team had "definitely felt like we made some progress recently".
"So overall, we need to be quite happy," he said.
"I think tomorrow will be a different day with different forecasts different track conditions. So it could also be a very, very different picture, and we just need to stay focused.
"Obviously we are in parc ferme, so it's not like we can improve the car a lot from today to tomorrow. But we will look into the smallest details and into the smallest things to see if we can pick up a tenths of two from today to tomorrow."
