Red Bull's weakness over kerbs and bumps was on display over the past four races in Miami, Imola, Monaco and Canada, with the RB20 inheriting some flaws from its predecessors that the team has yet to resolve.
The past races presented opportunities for Red Bull's rivals to catch up, partly through the Milton Keynes-based squad's difficulties and through their own upgrades. Lando Norris clinched a maiden win in Miami, while Leclerc took an emotional home victory in Monaco.
But ahead of a run of more traditional, high-downforce circuits like Barcelona, the Red Bull Ring and Silverstone, Ferrari driver Leclerc believes Red Bull will be firing on all cylinders again on tracks where the RB20 can fully stretch its legs.
"I feel like the strength of Red Bull will be more visible on a track like Barcelona," Leclerc said, after retiring from the Canadian GP.
"But let's wait and see. And behind [Red Bull] I think we'll all be pretty close."
George Russell, who qualified on pole in Montreal and took his first podium of the campaign in an improved Mercedes, said the fact that Max Verstappen still managed to win in Imola and Canada despite his handling issues suggested Red Bull will be a bigger force over the next European stretch of races.
"It's no secret they've struggled a bit with their car these last three races. Yet they've still won two of the last three," Russell warned.
"So I expect them to probably take a small step when we go back to the European races on more conventional circuits.
"We need to see how their performance turns out in Barcelona, but this pace increase that we've seen from us this weekend, it hasn't been a surprise to us because all the numbers back at the factory told us we're going to be finding a big chunk of performance with these upgrades.
"So Barcelona is going to be interesting for everybody, but I'm confident we can be in the fight."
McLaren's Norris, who battled Russell to finish second in Sunday's wet-to-dry spectacle, acknowledged that Mercedes will be the fourth player at the front from now on.
"If they're quicker in the next few races, too, and they've kind of joined the fight of Ferrari, Red Bull, and us, then it's only going to make our life more exciting," Norris said.
"More tricky and more stressful because now there will probably be eight cars which are fighting up there and challenging us all together. So it's exciting for us and probably everyone watching."
