McLaren team principal Andrea Stella has revealed that “pretty much the entire car” has been redesigned as it prepares to launch the all-new MCL60.

Following a difficult winter and a delay in development that has led to a tough first third of the season, McLaren has long had a B-spec car in the pipeline.

Stella confirmed to Speedcafe across the Monaco Grand Prix weekend his plans for its introduction, and that the car would be “very noticeably different” when it takes to the track.

What has now emerged is the extent to which McLaren has gone with the redevelopment which is so extensive it will now appear in three stages.

“Most of the upgrades we will see over the course of the following events, so there will be a major overhaul of the car that will be delivered across Austria, UK, and Hungary,” said Stella.

Explaining the thinking behind what will be delivered, Stella added: “Relatively soon at the start of the season, we realised the car needed a fundamental redesign.

“So this redesign actually involves, I would say, pretty much every single aerodynamic part. That’s why the upgrades will be spread over the course of a few races. We even had to redesign some parts under the bodywork.

“That’s also why it took some time to be in condition to deliver these upgrades. So I would say pretty much the entire car.”

Stella has confirmed the upgrades have yet to be tested in the simulator, but has outlined what he is expecting in terms of performance.

“They pretty much deliver more downforce with similar characteristics,” said Stella. “The key point is whether they will correlate trackside.

“But I think the correlation so far has been good. This generation of cars, in general correlation with development tools, is good, so we expect a few tenths of a second of lap time improvement.”

Before then, however, Stella is anticipating a tricky Canadian Grand Prix weekend due to the fact the car is simply not suited to the Circuit Gilles Villeneuve.

“In terms of upgrades here, we only have a rear wing, which is the version most suitable for the level of drag that you adopt at this track,” said Stella.

“We definitely prefer the characteristics of Barcelona because the car is strong in high-speed corners. Here we have no high-speed corners, quite a lot of low-speed traction, so it could be a bit of a struggle.

“We would certainly welcome some weather.”

Heavy rain is forecast for qualifying on Saturday which begins at 16.00 local time (21:00 BST; 06:00 AEST Sunday).