It's the seventh race of the season and by now we should know better than to get excited by Friday practice times. Engine modes, fuel loads and differing run plans can all conspire to paint a misleading picture on practice day, but in 2020 there's always a degree of intrigue when a car other than a Mercedes sets the fastest time.
On Friday, both Red Bull's Max Verstappen and Renault's Daniel Ricciardo beat championship leader Lewis Hamilton to the quickest lap. Yes, the margins were small -- just 0.093s covered the top three on a seven kilometre track -- but in a season when Mercedes has dominated over a single lap, it deserves some analysis.
Let's start with the obvious. Mercedes were the outliers at Spa-Francorchamps on Friday, finding themselves drawn into the ultra-competitive midfield battle when they would usually be around 0.5s clear at the front. Hamilton took third, but Valtteri Bottas was sixth fastest, with three different types of car ahead of him and the McLaren of Lando Norris just 0.006s behind.
We know Mercedes likes to save its engines during Friday practice by running low-power modes and typically the team covers up its pace with a heavy tank of fuel. At Spa-Francochamps an extra 10 kilos of fuel can account for 0.3s to 0.4s of lap time, so it's possible that a drained tank and the most aggressive engine mode will be enough to see Mercedes draw clear.
But look a little closer at the times and there appears to be more at play.
Engineers arriving at Spa-Francorchamps face an annual question of how much downforce to run on the car. Splitting the lap into its three sectors, ideally you'd have a skinny rear wing for straight-line speed in the first sector, a high-downforce wing for the high-speed corners in sector two and a skinny wing back on the car for the long straight in sector three.
Of course, it's not possible to change the wing mid-lap, so instead teams have to pick the best compromise for all three sectors. Mercedes experimented with a skinny wing in first practice, but ultimately opted for a fairly big wing in second practice when the fastest times were set and the long runs completed. By contrast, Red Bull opted for a relatively skinny wing, giving more top speed on the long straights of sectors one and three, but less downforce in the middle sector.
Those decisions were reflected in the sector times, with Hamilton conceding 0.206s to Verstappen in sector one, gaining 0.416s on the Red Bull in sector two and losing another 0.309s in sector three. So is it possible Mercedes simply got its sums wrong on wing settings and will revert to a skinny wing for the rest of the weekend?
Possibly, but dig a little deeper and Hamilton lost the majority of that 0.3s in the third sector in the final chicane alone. He admitted to a mistake under braking, but most of the time went missing under acceleration. A similar pattern was visible on the overlays of long runs of both Mercedes drivers versus Verstappen, suggesting the W11 has suddenly developed a relative weakness to the Red Bull in slow speed corners.
It's unlikely that weakness is related to the wing levels (especially as Mercedes was running more wing and therefore more downforce) and it will clearly be an area of focus for the team as it analyses potential setup changes in its factory-based simulator overnight. Solve the issue, and Mercedes will unlock a significant amount of performance on Saturday. Fail to do so and Red Bull might genuinely have the upper hand.
One other factor to consider is the weather, with rain currently forecast for Sunday. A skinny rear wing is fine for dry running, but if it rains the extra downforce could make a significant difference to performance.
Where did Renault's pace come from?
Renault was at the other extreme to Mercedes when it came to downforce levels, with Daniel Ricciardo running a relative slither of a rear wing in Friday practice. As a result, he held advantages of 0.4s over Hamilton in sectors one and three but gave away a whopping 0.779s in sector two.
Nevertheless, the Renault is certainly fast at Spa-Francorchamps and part of that is down to the steady performance gains the French manufacturer has found from its power unit this year. The solid pace was also evident on the opening two laps of Ricciardo's long run, but a hydraulics issue meant he had to bring his car to halt by the side of the track as a precaution.
But don't rule out Racing Point. It also had decent long-run pace, especially on the medium tyre, meaning Renault's place at the front of the midfield pack is far from guaranteed.
"Let's still be realistic," Ricciardo said. "Let's aim for a top six or something, that'll be a great result for us in qualifying.
"Today showed we got pace, but I'm not sure we can hold P2. I think we're still going to be in a good position tomorrow and there's no reason why we shouldn't... we'll focus on that, take the positive and focus on getting Q3 tomorrow."
What happened to Ferrari?
One team that wasn't near the front of the midfield was Ferrari. Charles Leclerc finished the session 1.6s off Verstappen's pace in 15th, with Sebastian Vettel a further 0.25s slower in 17th. Ferrari appeared to be running a low wing level and the sector times backed that up, with Leclerc losing 1.3s in the middle sector alone.
We know Ferrari is down on power this year, so running a skinny wing seems like a necessity here, but there was an expectation ahead of the weekend that some performance could be recovered in the middle sector. Clearly that didn't happen and team principal Mattia Binotto said it was down to both drivers struggling to get their tyres up to temperature.
"Generally speaking, if you don't find the right window on the tyres, certainly you do not have grip and you are not fast in sector two, and then you are slow in all three sectors," he said.
"We need to understand why we are not bringing the tyres to the right window of temperature and make sure we address it. It is the same situation on both cars, so it is not driver related. It is really the way we set up the car in order to find the right window on the tyres."
With the high-speed Monza next on the calendar, Ferrari needs to get a handle on how to run its car in low-drag configuration. Otherwise its difficult season could be about to get a whole lot worse.