The puzzle confounding Mercedes in Malaysia

"A puzzling Friday" was the verdict coming from the Mercedes camp after Friday practice for Formula 1's final Malaysian Grand Prix.

On a circuit where it dominated on pure pace last season, and would have won easily but for Lewis Hamilton's spectacular engine failure in the race, F1's multiple reigning champion team was nowhere on the 2017 Friday practice timesheets.

Lewis Hamilton and Valtteri Bottas visibly looked to be struggling for grip throughout Friday's dry second session. Both went off while lapping on the soft tyre: Bottas wandering wide through the gravel at Turn 11, Hamilton spinning off after clipping the inside kerb at Turn 7.

And they fared little better while attempting qualifying simulations on the super-soft compound. Hamilton wound up 1.416s off the pace set by title rival and Ferrari driver Sebastian Vettel; Bottas was another 0.043s further back; both were slower than Fernando Alonso's upgraded McLaren-Honda.

Pure pace ranking

1. Ferrari (Vettel) 1m31.261s
2. Red Bull (Ricciardo) 1m32.099s
3. McLaren (Alonso) 1m32.564s
4. Mercedes (Hamilton) 1m32.677s
5. Force India (Perez) 1m32.862s
6. Renault (Hulkenberg) 1m33.060s
7. Williams (Massa) 1m33.394s
8. Toro Rosso (Gasly) 1m34.043s
9. Haas (Grosjean) 1m34.118s
10. Sauber (Wehrlein) 1m35.246s

Malaysia's Sepang circuit should be a Mercedes stronghold under normal circumstances. It's a track where downforce and engine power rule the roost, elements Mercedes usually enjoys in abundance.

Even more than Barcelona or Silverstone, it's a circuit that should show off the general strength of a Formula 1 car. If that's the case, the Mercedes W08 has suddenly and unexpectedly been found seriously wanting.

This was undoubtedly Mercedes' worst Friday of the season. Worse than Russia, where trouble with the ultra-soft tyre left it 0.670s off the pace; worse even than Singapore (0.703s) and Monaco (1.153s), the low-speed street circuits on which it usually struggles compared to its main rivals.

"We struggled from the get-go this morning in the wet, in the dry, on all tyres," Mercedes team boss Toto Wolff told Sky Sports F1. "We have to find out overnight what it is.

"You can compare Malaysia a little bit to Silverstone, where we have been very good. We've been very good in the high-speed; we are not at all good in the high-speed here.

"There is a fundamental issue in the car that we need to find out and they are very complex, so it can be a tiny detail that just unsettles the car.

"At the moment, the car is unbalanced and you slide all over the place - the fronts and rears you overheat them and then nothing goes anymore. There is a gremlin in the car."

Wolff ruled out tyre management - in the manner that hurt Mercedes at Sochi - calling the overheating a "consequence" of its problems here.

"It's a bit up and down with our car that we seem to be performing exceptionally good on some tracks," he added. "Monza was one of them, where we were a second ahead, and Silverstone the same, and then others we have these moments where we are lacking the understanding why we are not performing."

The comparison to Silverstone is interesting. Although it would seem similar in its basic layout - mainly straights and fast corners - there are some key differences at Sepang.

Says one senior paddock engineer: "Sepang has more low-speed corners than Silverstone. The car has got to be good in low-speed, medium-speed and high-speed. The car has to be strong at all different rideheights here."

Mercedes is alone among the leading teams in not adopting a high-rake (high rear rideheight) design philosophy, which some leading technical chiefs say is the right way to go if you want to make the most of the larger floors and diffusers encouraged by this year's new regulations.

"Often Mercedes can underperform over one lap but still look competitive on the longer runs. It is rare to see the team totally off the pace in all conditions like this"

Mercedes has often struggled to balance its car through a wide range of cornering challenges this season, with Hamilton referring to how "peaky" the car can be, meaning it has a narrow set-up window in which it can perform at its best.

"Downforce is king here," adds the engineer. "It's a good reference for car development - if you've got a peaky aero map this will be a difficult circuit for you. If you've got any weakness - entry, mid, or corner exit - you will hit it in those 180-degree corners."

There are plenty of long-duration corners on this track - Turns 1, 2, 9, 11 and 14 are all relatively low-speed (not Mercedes' natural strength) and long enough to show up imbalances in the car.

"The car balance itself didn't feel too bad," reported Bottas, who recorded two laps within 0.013s of each other, suggesting he was lapping about as quickly as his car could go in FP2. "It's just a question of overall grip."

Combining the Mercedes drivers' best sector times lifts the team above McLaren (by 0.012s) and within 1.366s of the best Ferrari could have theoretically managed, but that's still the biggest deficit of the season so far.

Wolff remarked after the session that Mercedes didn't know why it had suffered "one of the worst Fridays I can remember", but it looks as though it is indeed something fundamental.

The longer runs were cut short by Romain Grosjean's high-speed crash over a dislodged drain cover, but Vettel, Kimi Raikkonen, Daniel Ricciardo and Bottas all completed some high-fuel running on the super-soft compound before the red flags flew.

Raikkonen was a tenth faster on average than Vettel over a three-lap run, eight tenths clear of Ricciardo's Red Bull (which did five laps), and over 1.8s quicker than Bottas, who was slower over his four-lap run than Esteban Ocon's Force India and the works Renaults of Nico Hulkenberg and Jolyon Palmer.

Often Mercedes can underperform over one lap but still look competitive on the longer runs. It is rare to see the team totally off the pace in all conditions like this.

"We need more grip - that's going to be the key," added Bottas. "We're definitely missing overall grip, just sliding around, especially in all the high-speed corners.

"And this kind of track, if you slide a lot, you put so much energy through the tyres, you overheat the tyres and it gets tricky.

"Honestly, the balance didn't feel bad, the car felt quite okay to drive, just not enough grip."

"Mercedes is bound to improve - you don't win three consecutive world championship doubles by accident - but there's no doubt it now finds itself in serious trouble on a track where it should be dominant"

Mercedes has brought a substantial upgrade to the W08 for this race, including revised front wing, 'spoon' deflector, bargeboards and floor, predicted to be worth 0.15s. Perhaps this latest update has thrown the car out of its natural operating window.

Losing the morning session to rain would only have hampered efforts to understand the effects of this upgrade on the car in the real world.

"One thing we know is the cars are really sensitive," says Ricciardo, who also expected Mercedes would "lead the pack" on Friday. "They have more grip, so they should be easier to drive and easier to feel the grip, but it's easy to go too far and overstep it.

"It seems to cost a lot of laptime, when you slide with these cars. It's still a bit of a puzzle we're trying to solve."

A puzzle that appears to have seriously and unexpectedly vexed Mercedes in Malaysia. The onus will now be on the engineering team to come up with solutions to try in final practice, to whip the W08 into shape in time for qualifying.

Mercedes should take heart from the fact Ferrari overturned a massive 1.983s deficit to Red Bull after Friday practice in Singapore for Vettel to snatch pole position by three tenths on Saturday. Massive performance swings are realistic if you know how to retrace your steps and unpick the mess you've made.

Red Bull was seriously fast in the wet in FP1 here - more than 1.7s clear of Ferrari and over 2.5s ahead of Mercedes on the intermediate tyre, which reinforces the team's feeling that it has solved its early-season aerodynamic problems to produce the best chassis on the grid, which is now a serious threat whenever the relative weakness of its Renault engine is negated, which won't be the case here unless it rains again.

Ferrari enjoys the benefit of a much more potent engine than Red Bull's Renault, and the Prancing Horse also enjoyed an unexpectedly strong Friday in Malaysia, after struggling in practice at the last two events at Monza and Marina Bay.

The SF70H's revised bargeboard, floor and power unit cooling package - which also allows the Scuderia to run tighter and more aerodynamically efficient bodywork at the rear of the car - appears to be working well, and Ricciardo was certainly surprised to be more than eight tenths adrift of Vettel's pace.

"It would be nice to carry that through the whole weekend but I don't know what other people were doing today," Vettel said. "It looked like they [Mercedes] were both struggling the morning and afternoon.

"I'm pretty sure they will be fine tomorrow. In the end, it's Friday, when you can play around and try some things."

Of course Friday is a day for experimentation, but it also sets the tone for the rest of the weekend. Mercedes was well off the pace in all conditions, and if rain hits Saturday morning's session, but not qualifying or the race (or vice versa), the team could find itself stuck in a hole.

Mercedes is bound to improve, of course - you don't win three consecutive world championship doubles by accident - but there's no doubt it now finds itself in serious trouble on a track where it should be dominant. Trouble that simply turning up the engine for the business end of the weekend, as usual, will surely not be enough to escape.

"Now we need to find out if any of the new parts actually made the car worse," reckoned Bottas. "We were supposed to have quite a good step, but it didn't seem to happen. The team is reviewing everything and we need to make sure we choose the right bits for tomorrow."

That Mercedes is potentially stuck in an aerodynamic development trap will be music to the ears of Ferrari and Sebastian Vettel, who could receive a welcome and unexpected boost to their championship ambitions if Mercedes is unable to solve this puzzle.

And that would also be great news for those who feared this title battle was in real danger of fizzling out.