Ferrari left the opening week of testing looking like the benchmark for the rest of the field. But how will the final four days shape up?
Ahead of the resumption of testing on Tuesday at the Circuit de Catalunya, we look at the five things we expect to see or learn by the end of the week.
Ferrari flexing its muscles
What made Ferrari's lap times in the opening week of testing so impressive was that they were set on relatively hard compound tyres and relatively high fuel loads. In the second week we should see something closer to a qualifying simulation and it's entirely possible that the SF90 breaks the lap record of 1:16.173 set during qualifying for last year's Spanish Grand Prix.
In the first week of testing, Charles Leclerc set a 1:18.046 on the C3 compound - the third fastest tyre on offer - and according to Pirelli there should be another 1.2s of performance locked away if Ferrari bolt on a set of C5 tyres. The reality, however, might be a bit different with some teams, such as Mercedes, already struggling to find the full 0.6s performance advantage expected from each compound.
In previous years, Ferrari has dedicated the final two afternoons of the second week of testing to qualifying simulations and race simulations. Last year the team even set up a dummy grid spot just outside its garage to mimic the moments ahead of the race when the car sits on the grid. Keep an eye on the times either just before or after lunch to see whether the Ferrari has the raw pace to match its irst week hype.
Mercedes aero update
Although Mercedes completed the most mileage of any team in the first week, there was no disguising its disappointment with its lack of pace. An aero upgrade will bring the car much closer to its Melbourne specification this week and the hope is that it will iron out some of the rear-end instability the drivers were experiencing at high speed.
"There's definitively a lot of potential, but we're not yet quite there," Valtteri Bottas said last week. "I sense a bit of an excitement in the team, to discover more about the car and we're really, really trying to improve it, because at this moment it looks like we're not miles ahead of everyone. It seems like Ferrari is, at this point, in a better place, but I think that motivates us. Obviously we'd love to be ahead in Melbourne, but it's too early to speak about that."
However, it should be noted that the upgrades coming in week two are not a direct response to what happened in week one. These updates would have been planned for over a month and based on the team's understanding of the car in the wind tunnel prior to testing -- so any nasty surprises last week will either have to be engineered out of the car with setup changes or addressed with updates at the early races.
Either way, if you were to back a group of engineers to find a solution to a slow start to testing it would be the five-time world champions.
Can Honda keep up with Mercedes and Ferrari?
Although Red Bull didn't attack the track on low fuel and soft tyres in the first week, the car looked competitive. Over longer runs it seemed to be in a similar ballpark to Ferrari, hinting at the promise from the new RB15 chassis. However, in recent years the Red Bull has looked a match for the top two in race trim but has almost always come up short in qualifying. Red Bull always put the lack of one-lap pace down to its previous engine supplier Renault and it is hoping a switch to Honda power will help cut that gap in 2019.
In the first week of testing the Honda looked reliable and both the Red Bull and the Toro Rosso were a match for the Ferrari- and Mercedes-powered cars in the speed traps. However, when it comes to stretching the performance of the power unit in qualifying mode, Honda is not so confident.
"We think we are still behind the other manufacturers," Honda technical director Toyoharu Tanabe said. "Not a small amount so we will try to catch up this gap over this year."
Keep an eye on the speed traps when the teams attempt qualifying simulations to see how big the deficit is to the top two.
How bad is Williams' situation?
Missing the first two and a half days of testing was a major setback for Williams, but the concern is that the lost mileage was just the tip of the iceberg. The team has yet to attempt any performance running, but the murmurings from Grove is that the wind tunnel numbers are unlikely to be enough to elevate Williams from the back of the grid.
There was also speculation over the future of technical boss Paddy Lowe last week, who joined in 2017 as a shareholder. The delay to the 2019 car happened under his watch and did not seem to be communicated as openly as perhaps it should have been with the team's top management. Lowe is due to speak to the media this week and it will be interesting to hear his take on the situation and, ultimately, why the start to the year has gone so wrong.
Meanwhile, there will be plenty of attention on the timing screens to see whether the FW42, which carries the hopes of two very talented drivers in George Russell and Robert Kubica, can finally offer the embattled team something to smile about.
Has Renault broken free of the midfield?
In recent years there has been a void between the top three teams and the rest of field and it is Renault's aim this year to start filling it. The early signs are good, with Nico Hulkenberg setting the fastest time of week one without pushing the package near its limits.
"It's been useful trying different things, getting new feelings, so that's been positive," Hulkenberg's new teammate Daniel Ricciardo said on Thursday. "There's certainly more there, there's a lot more potential still to extract. It's all close at the moment, but we're looking quite consistent. We're still running a little bit conservative but we'll see how it goes when we ramp it up."
Renault is likely to face tough competition from the Ferrari-powered teams of Alfa Romeo and Haas, which both used harder compounds to set their most impressive times in week one. Race simulations and qualifying-style runs should help cast more light on where those three teams stack up and just how big the gap is to the top three.