A big weekend - and a big chance - for Verstappen
Red Bull's decision to switch their drivers - Verstappen moving up, Kvyat moving back to Toro Rosso - came of course after the latter's double-collision with Ferrari's Sebastian Vettel in Russia. But this move is based on far more than just events in Sochi: Red Bull are betting big on Verstappen, and have reportedly extended their contract with the Dutchman as part of his move.
What happens next will be fascinating. How will Verstappen fare against three-time Grand Prix winner Daniel Ricciardo? Will he prove an immediate frontrunner, and carry the fight to the likes of Williams and Ferrari - and possibly even Mercedes?
For all the hype, the man at the centre of it all seems unflappable. "I'll take it quite relaxed and see where it goes," was Verstappen's almost nonchalant verdict. "I'll study procedures and work with the mechanics, and hope the car will be faster [than the Toro Rosso].
"They are a competitive team and I'm a competitive person, so I hope the performance matches up. The most important thing is to score points. I don't think there is any more pressure, but of course I will be trying to achieve my best."
While he's been vocal about things at Toro Rosso when the need arises, Verstappen hasn't made many serious mistakes since he joined the Formula One fraternity in 2015. One year on, he is driving for one of the best teams on the grid. No other driver in history has achieved so much, so young. Where he goes from here will be intriguing to watch.
Have Mercedes fixed their reliability woes?
The other man in the spotlight will be Lewis Hamilton, who enters the weekend firmly on the back foot in his fight against Mercedes team mate and championship leader Nico Rosberg.
The Briton's cause has been set back heavily, of course, by recent technical gremlins - he has started 22nd and 10th in the last two races, while Mercedes said it was a ‘miracle' he reached the chequered flag in Russia due to having zero water pressure. Rosberg too suffered reliability concerns in Sochi, prompting some furious work behind the scenes from the team. So have they got to the bottom of the issues?
"The highest priority is to come back with our MGU-H problem solved," Mercedes' executive director (technical) Paddy Lowe admits. "The team have been working day and night to understand it and we're targeting a clean weekend all round."
Hamilton has been travelling a lot since Russia, and keeping his spirits up despite the 43-point deficit to his team mate.
"Every weekend we've got the car into a great place set-up-wise - I just haven't been fully able to exploit it," he says. "So the glass is half full for me. It will be a big challenge but there's a long way to go with 17 races left and, if the last four are anything to go by, there's a lot more still to come from us. The team has been on it 24/7 since returning from Russia so I'm confident they'll get to the bottom of the problems we've been having. I know I'm still quick."
Rosberg, meanwhile, is taking nothing for granted. "Sport is all about ups and downs and being mentally prepared to bounce back stronger when they come," he says. "With a season this long you have to just take things race by race. There are 425 points still up for grabs - and anything can happen yet. Now, it's Barcelona. I got my first pole and win at this circuit last year and I'm connecting really well with the car at the moment, which is great as it gives you this awesome confidence to push the limits."
Team boss Toto Wolff says Mercedes have an added cause for concern in Spain - updates on the cars of their chief rivals.
"We're going to see some big upgrades from the different teams and power unit suppliers over the next few races," he said, "so now is the time we can truly assess the pecking order. Barcelona will be an interesting weekend from that perspective."
WATCH: Get to know the Circuit de Barcelona-Catalunya
Will McLaren take a big step forward?
Barcelona is traditionally the place where everyone brings update packages following the first flyaway races, but fresh from their first double-points score in Russia, McLaren in particular have grand designs - and high hopes - for their MP4-31.
This will boast new wings, new bodywork and a new floor, in an attempt to tame the car's edginess and boost its prospects for breaking into Q3 after coming so close in Sochi.
"I don't know how it will go for Barcelona, and I don't want to create any expectation," sporting director Eric Boullier says. "But Monaco afterwards should suit us, although that race can also be very unpredictable."
Honda's power unit, meanwhile, still lacks top-end performance and both Fernando Alonso and Jenson Button were obliged to save fuel in Russia, but as the Japanese engineers prepare a major engine upgrade for later in the season McLaren have been bringing new parts to every race and showing progress after their problems in 2014. Last time out, only the need to conserve fuel prevented the black cars from matching fourth- and fifth-placed Williams' race pace, according to team sources.
"It's coming up, it's good," Boullier added. "We keep bringing every race some developments, so the team is putting a lot of effort in – both McLaren and Honda – so good to see little by little we are closing."
Changes expected along the pit lane
McLaren are by no means the only team bringing in updates at Barcelona. Indeed there is a saying in Formula One racing that if you're quick around Barcelona, you'll be quick everywhere - which is why so many teams push for a performance surge in Spain.
Ferrari will have a new rear wing to try, in addition to the latest engine upgrade which appeared in Sochi. This is a crucial race for the Scuderia, in which they must prove that they really are making progress against Mercedes when the on-track evidence instead suggests that the gap between the two top teams has increased slightly this season.
Force India will have a big upgrade comprising a new front wing, floor and bodywork, in a bid to turn around what has been a slightly disappointing start to the season.
At Manor, Pascal Wehrlein and Rio Haryanto are putting their faith in a new package that comprises new wings and floor, as Renault brings new front and rear wings for Kevin Magnussen and Jolyon Palmer.
The beleaguered Sauber won't have any new aero parts, but will be running the latest version of Ferrari's 2016 engine which debuted in Russia, as will Haas. Toro Rosso, however, will stick with the 2015 power unit as their supply deal is more limited.
Tyre choices will be a factor…
Once again, there's disparity in the teams' choices of tyre compounds. Mercedes, Williams and McLaren have opted for one set of hards, five of mediums and seven of softs; Ferrari for one, four and eight; Red Bull for two, four and seven (Verstappen and Kvyat will use each other's choices); while Haas will have a split garage as Romain Grosjean and Esteban Gutierrez have opted for different selections.
"The soft will be essential for qualifying but not be a great race tyre, so determining the optimum strategy will be a focal point," Mercedes' Paddy Lowe says.
The high-downforce Circuit de Barcelona-Catalunya has a generally quite rough surface and generates high energy loads on the tyres, especially the front left which gets a lot of stress in corners such as the long Turn 3 right-hander, and is thus front-limited. Wear and degradation are high, so multiple pit stops are expected.
"Spain always provides a very big test for the tyres due to the high energy loads that the circuit generates, and this year that will especially be the case with most teams having favoured the softer compounds in their selections," Pirelli's motorsport director Paul Hembery points out. "Of course they will be able to rely on the data accumulated during pre-season testing, but at this time of year we expect conditions to be much warmer. As a result we should see high wear and degradation leading to several pit stops, which of course opens up a very large number of strategic variables for the Grand Prix."
…and the weather could be too
Indications are that showers could disrupt proceedings over the course of the weekend. Light rain is forecast for Thursday, with more persistent showers expected to strike during Friday's running - while on Saturday the chances of rain increase in the afternoon, meaning it could potentially arrive during qualifying.
The same is true on Sunday, when - despite anticipated temperatures of around 20 degrees Celsius - showers are forecast for the afternoon, raising the prospect of a race run in changeable conditions.
The race itself will start at 1400 hours local time (1200 GMT) on Sunday, and run over 66 laps or 307.104 kilometres (190.834 miles).