Traditionally this is the race where everyone brings the upgrades they have been working on ever since they launched their cars at the start of the season. It's where the frontrunners seek to move further ahead; where those giving chase plan to close the gap; and where a truer picture of the pecking order emerges.
Mercedes have enjoyed an advantage of around six-tenths of a second per lap over their principal rivals Ferrari and Red Bull in terms of raw speed, though their race pace has been even better. And they are determined to pull further ahead here.
"It's often said that a car which performs well in Barcelona will be a great car for the season, so we're looking forward to seeing where we stand relative to the competition," says Paddy Lowe, executive director (technical). "There has been no sense of complacency or backing off just because our car has shown strong performance in the opening few races. The objective is to not only match, but to better the development rate of our rivals and to build on our lead in both championships."
Lewis Hamilton had not won in either Malaysia or Bahrain prior to 2014, and he hasn't yet won in Barcelona either. He plans to put that right this weekend.
"It's been good to have a bit of a break between races," the 2008 champion says. "But after three great weekends in Malaysia, Bahrain and China I'm obviously keen to get on to the next one and continue that positive momentum into the next leg of the season.
"I've never won in Barcelona but I'm in a good place right now and I'm hoping that this will be the year."
Nico Rosberg, meanwhile, is keen to turn the Hamilton tide, after losing three times to his team mate following his own victory in Melbourne's season-opener.
"It's only now that we can slowly begin to get an idea of how the different cars stack up in terms of performance," the German says.
Meanwhile, Ferrari hope to keep building on the momentum they got going in China, where Fernando Alonso scored their first 2014 podium after the disappointment that was Bahrain. The Spaniard remains cautious ahead of his home race, however.
"The car was under-performing in many areas - it was not just one problem," he said after finishing third in Shanghai. "We need to be more efficient, have better aerodynamics, better traction, better power. We lacked some big performance in the first races. In China it was nothing really big in one area, just small steps here, small steps there - better power delivery, better software, putting everything in place, all the settings, and giving a little bit more aero efficiency and a little bit more power.
"But the other teams will bring a couple of tenths to Barcelona, so we need to bring a couple of tenths, plus something. That's the challenge we are facing now. It's not that we need to develop the car at a normal rate; we need to do the normal development, plus something."
Red Bull arrive with great optimism as power unit supplier Renault expect a big upturn in performance thanks to changes to their turbo V6. In particular, boss Christian Horner wants to see significantly improved straightline speed. He is targeting victory to kickstart the team's title aspirations.
"We've got to beat Mercedes here if we're going to make a championship of it," he admits. "We've got to take the fight to them. We're going to give it everything. I believe we can take the fight to them, we just can't concede too much more ground.
"We were 22 km/h slower on the one-kilometre straight in Shanghai - that represented almost 100 metres that we were giving away just on the straight. That's where we've got to improve, it's quite simple. We know where we've got to fix our issues and hopefully there are some steps towards that in Barcelona."
At Renault, head of track operations Remi Taffin explains why Red Bull, Lotus, Toro Rosso, and Caterham are hopeful of performance improvement: "While there are not many visible hardware upgrades, there are significant improvements to the software that should further enhance driveability and therefore overall performance. Yet again we have also moved forward in energy management and efficiency so we are hopeful our upward trend will continue in Barcelona."
World champion Sebastian Vettel will also be handed a new chassis for this event, though Red Bull stress it is a routine introduction rather than a reaction to the German’s current form. He’ll be hoping that significant upgrades to the RB10 not only help move the team further up the grid, but also help him take the fight to impressive team mate Daniel Ricciardo.
On paper Williams are the most improved team since 2013 but the luck has yet to run with them. A small increase in performance could push them past Ferrari and Red Bull, and they come to Spain with many aerodynamic changes to the FW36. Right now nothing could be better for the team than for either Felipe Massa or Valtteri Bottas to repeat Pastor Maldonado's astonishing 2012 victory.
"The teams and drivers know the track well, meaning we can gain a lot of accurate data on how the upgrades are working," says head of vehicle performance Rob Smedley. "The track itself has a very good mix of long straights, some high-speed corners like Turn 3 and some more technical and slower sections. Turn 3 is important for managing tyre wear so it's something engineers and drivers have to monitor. We feel prepared going in to the weekend."
The battle between Force India and McLaren is one of the highlights of the season thus far, and both teams will have revisions.
"It's encouraging that we have performed well across a wide range of circuits, so I'm optimistic that we can maintain our competitive form in Barcelona," team owner Vijay Mallya says. "China has never been an especially strong track for us, so to come away with 10 points was a very good effort. We also expect our car to perform better in warmer conditions and there are some upcoming races that will play more to our strengths. At the same time we know that Formula One never stands still and Barcelona is always a pivotal moment in the development race, but I'm optimistic we can keep up our momentum."
At McLaren, Jenson Button says: "For us, it's not simply about bringing new parts to the circuit: it's about understanding and unlocking the car's secrets, and using that understanding to take bigger steps with performance. We're still at the early stages with our car, and, for us, it's less about the components that we fit to it, and more about the bigger picture - finding a useful direction, gaining trust in our measurements and pushing ahead."
Further back, while all of the smaller teams will similarly have updates, Sauber are placing their hopes on revised engine software, which is expected to squeeze more out of the Ferrari V6, and a lightweight version of the C33 chassis that has pared off 15 kg. Add to that a revised aero package, and it's easy to see why the Swiss team are hopeful of getting into the midfield scrap.
Pirelli are bringing their two hardest compounds for what they describe as a ‘high-energy' circuit: the orange-marked hard and the white-marked medium.
The familiarity of the Catalan track makes it a good place to introduce updates designed primarily to enhance downforce, and that in its own way affects tyre performance as it adds to the demands placed upon them.
"It's often said that Barcelona provides the most accurate representation of the form a season will take, because a car that performs well in Barcelona should perform well everywhere," explains motorsport director Paul Hembery. "The same is true of the tyres, because the Spanish circuit is one of the most demanding circuits we race on all year. Long and fast corners such as Turn 3 put a huge amount of energy into the tyres, as a result of which degradation is high. The track surface is also quite abrasive, and ambient temperatures can be high, which increase the workload on the tyres further. In the past we've seen up to four pit stops in Spain. With the changes we have made to the tyres this year, we would now hope to see no more than three for the majority of drivers."
Pirelli will also run another post-race tyre test in Barcelona, this time utilising Force India, McLaren, Toro Rosso and Sauber.
"We made a solid start to our preparations for next year with the first dedicated in-season tyre tests in Bahrain. We're looking forward to building on that work in Spain after the Grand Prix," Hembery added.
The weather in Catalunya is expected to be settled, with sun and ambient temperatures in the mid-20s Celsius forecast for the weekend. The circuit meanwhile is largely unchanged from last year, apart from minor work on kerbs and asphalt replacing the gravel run-off at Turn 11. Two DRS zones will again be used. The first begins 40m after Turn 9, with the detection point 86m before the same corner. The second zone's detection zone is on the safety car line at the entry of Turn 16, with activation occurring 157m onto the main straight.
Sunday's race will run over 66 laps or 307.104 kilometres (190.834 miles), and will start at 1400 hours local time, which is two hours ahead of GMT.