Following the pre-season test in Bahrain, without a doubt, Red Bull emerged as the clear favourite ahead of Mercedes given the struggles of the F1 champions.
Mercedes had been hampered by new aerodynamic regulations that had targeted the floor of the car, in particular, and affected its low-rake philosophy compared to Red Bull's higher-rake design.
While Mercedes emerged from the season-opening race in Bahrain with a surprise win for Lewis Hamilton due to its tactical acumen despite Red Bull clearly possessing the fastest car, the gap over the following three races has shrunk considerably.
From Hamilton being almost four-tenths of a second adrift of Max Verstappen in qualifying for the Bahrain Grand Prix, the seven-time champion marginally shaved their duel ahead of the race in Spain.
After four races, Hamilton has a 14-point lead over Verstappen, while Mercedes is 29 points clear of Red Bull in the constructors' standings.
Explaining the rapid turnaround, trackside engineering director Andrew Shovlin said: "It's fair to say that following the Bahrain test we were struggling a bit with the car.
"We hadn't got it into a good window, and the drivers were talking about how they didn’t have the confidence to carry the speed into the corners.
"The car wouldn’t even turn well into the corners, it was difficult to get it round some of the tight corners there and we were losing time.
"Also the rear end was struggling when we got on the power, it was quite oversteery, so we had a lot to put right.
"Now, there was a great deal of work in Brackley and in Brixworth on the power unit side, because we could see a few things in terms of the handling of the car that wasn’t where we wanted it to be.
"Equally, on the power unit side, there were a few areas that we could improve there in terms of the delivery of that power.
"So, most of it was really hard work and finetuning, [and] we had numerous sessions in the simulator trying to get everything in the right window.
"When we went back to Bahrain [for the race], while we weren’t the quickest - that was clearly Red Bull and we saw that in qualifying - we did have a car in a place where we could actually compete with them."
Expanding further, Shovlin added: "We had improved the long runs significantly and that was really the thing that allowed us to win that first race in Bahrain.
"We also had an update kit on the car in Imola, and we are looking for small improvements really, there is so little between us and Red Bull that every few milliseconds we are chasing after.
"So, in summary, it isn’t one thing. A bit of it is performance that we are bolting on with upgrades but a lot of it was really just understanding the issues and getting the car into a good place and allowing the drivers to have a car that they have confidence in and they can push to the limits.
With an ominous warning for Red Bull, Shovlin concluded: "We are going to keep doing that because I am sure there is more to come.”
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