Has Ferrari dropped the ball in Brazil?

Ferrari trailing Mercedes on a Formula 1 Friday is no great surprise based on previous form in 2015, but the magnitude of the deficit in Brazil certainly raised some eyebrows.

Sebastian Vettel's Ferrari lagged behind the fastest of the two Mercedes (driven by Nico Rosberg) by almost a full second in practice for the Brazilian Grand Prix. That's a large gap around what, at 2.677 miles, constitutes the shortest lap on the F1 calendar.

Team-mate Kimi Raikkonen was a further tenth and half adrift, suggesting Ferrari is struggling for single-lap pace so far, on what turned out to be a surprisingly tough day for many drivers.

Sure, Lewis Hamilton was only half a second up the road from the best of the Ferraris in second practice, but we can safely presume he would be much closer to team-mate Rosberg had he set his engine correctly for his single-lap run.

Hamilton dropped time in the first two sectors, particularly three tenths in sector two, which is a lot between team-mates on a lap this short.

PURE PACE RANKING

1. Mercedes (Rosberg) 1m12.385s
2. Ferrari (Vettel) 1m13.345s
3. Red Bull (Ricciardo) 1m13.585s
4. Williams (Bottas) 1m13.603s
5. Lotus (Grosjean) 1m13.634s
6. Force India (Hulkenberg) 1m13.710s
7. Sauber (Nasr) 1m14.134s
8. Toro Rosso (Verstappen) 1m14.226s
9. McLaren (Button) 1m14.644s
10. Manor Marussia (Stevens) 1m16.501s

Unlike Raikkonen and the two Mercedes drivers, Vettel attempted a second flier on his same set of soft tyres, improving fractionally in sectors one and three of the lap but dropping time in the twists of the middle.

Rosberg ended day one on top © LAT

If you add his best sectors together he improves by half a tenth overall, so he can take heart from the possibility he simply didn't get his first lap together.

Nevertheless, Ferrari was struggling on Friday, and Vettel's comments afterwards supported that theory.

"I think everyone is struggling a lot on the tyres," he said. "I think they are quite tricky to work with. I think it's slippery for everyone.

"I tried to do the best I could, [but] the car is moving around quite a lot. I'll give you my number later, and if you see a guy called 'Grip', you just pass on my number..."

Raikkonen said his car "didn't feel too bad on one lap", so perhaps there is not one glaring set-up issue that accounts for Ferrari's lack of relative speed.

Certainly many drivers complained of a lack of grip on Friday. The Interlagos circuit was resurfaced ahead of last year's grand prix, and the Pirelli tyres generally worked well with the new asphalt.

This season, the suggestion is that the surface has lost some of its 'micro-roughness' thanks to the smoothing out of some of the stones in the asphalt that would ordinarily help the rubber generate grip through abrasive contact, and that the track is even "crumbling" - in Rosberg's words - in places.

The strange thing is that Ferrari looked reasonably good on a low-grip surface in Mexico last time out, so perhaps the Scuderia did drop the ball in some way.

Raikkonen complained of a "messy" day © LAT

We will know more after final practice on Saturday morning, once the teams have had another crack at their qualifying simulations.

It is often said that Fridays do not matter in F1, but that's not strictly true. It gives you a platform from which to build the rest of your weekend, and if it doesn't go smoothly that's simply more work to do in a shorter period of time to catch up to your rivals.

Ferrari has usually had a far stronger car in race trim relative to Mercedes this year, but the longer runs here do not make for prettier reading for Vettel and co.

Hamilton averaged 1m16.953s on the soft tyre over an 11-lap run (fractionally faster than Rosberg's 1m17.075s average over 12 laps), while Vettel's 14-lap run put him half a second per lap adrift of the best of the Mercedes.

Of course we don't know the exact fuel loads the cars were running, and traffic always has an effect on a circuit as short as this one, but Ferrari would certainly expect to be closer than that on any other Friday run.

Ferrari split the workload and stuck Raikkonen out on the medium tyre (reckoned by Pirelli to be 1.2s slower on average than the soft), but his average pace over a mammoth 17-lap stint was over a second slower than Rosberg's on the same tyre.

Rosberg averaged 1m16.870s over nine meaningful laps, while Raikkonen's average laptime was 1m17.910s. Even if you take the Finn's best nine laps to compare directly against Rosberg's, he trails the Mercedes by 0.702s per lap...

The Scuderia is struggling in Brazil at the moment, and unless it can find a breakthrough overnight it is more likely to be fighting off a challenge from Red Bull and Williams than putting Mercedes under any real pressure.

Ricciardo hoped for more power from the revised Renault © LAT

Daniel Ricciardo was not overly enthused with Renault's updated power unit, but his long-run pace on the soft tyre was less than a tenth adrift of Vettel's, though his average is taken over a substantially shorter six-lap run.

Team-mate Daniil Kvyat (running the previous spec engine) matched Ricciardo's pace on the soft to the tenth over a longer 10-lap run, which suggests Red Bull could realistically be on Ferrari's case here.

Ricciardo produced a more representative run on the medium rubber, and was only a tenth slower than Raikkonen's average. However, Kvyat lapped within 0.025s of his earlier pace on the medium tyre over another 11-lap run, suggesting the RB11 is currently 0.361s per lap faster than the Ferrari on the slower tyre, notwithstanding the fact Kvyat was out on the medium a bit later than Raikkonen, when the track should have theoretically been a bit faster.

"Top five for us on this track is really good," said Ricciardo. "I'm not sure if we can expect to stay there tomorrow, but that's the target. I think Williams and Ferrari will show a bit more speed tomorrow, but it's not a bad day.

"The engine was reliable, sure I want a bit more power from it - it's not [got] as much as we would like - but at least we got some good laps and some good information."

Ricciardo is probably right to be wary of Williams, which usually makes a decent step from Friday to Saturday, particularly over a single lap. The FW37 is also working the medium tyre particularly well, and Valtteri Bottas was able to lap two tenths per lap faster on average (over a seven-lap stint) than Kvyat.

SOFT TYRE LONG-RUN RANKING

1. Mercedes (Hamilton) 1m16.953s (11-lap average)
2. Ferrari (Vettel) 1m17.466s (14-lap average)
3. Red Bull (Kvyat) 1m17.524s (10-lap average)
4. Williams (Massa) 1m17.799s (8-lap average)
5. Lotus (Grosjean) 1m17.916s (11-lap average)
6. Force India (Perez) 1m18.153s (8-lap average)
7. Toro Rosso (Sainz) 1m18.238s (11-lap average)
8. McLaren (Button) 1m18.652s (9-lap average)
9. Manor Marussia (Stevens) 1m21.798s (14-lap average)
*Sauber did no long runs on the soft tyre in FP2

MEDIUM TYRE LONG-RUN RANKING

1. Mercedes (Rosberg) 1m16.870s (9-lap average)
2. Williams (Bottas) 1m17.349s (7-lap average)
3. Red Bull (Kvyat) 1m17.549s (11-lap average)
4. Ferrari (Raikkonen) 1m17.910s (17-lap average)
5. Toro Rosso (Sainz) 1m17.929s (10-lap average)
6. Force India (Perez) 1m18.048s (6-lap average)
7. Sauber (Nasr) 1m18.201s (16-lap average)
8. Lotus (Grosjean) 1m18.248s (7-lap average)
9. McLaren (Button) 1m18.597s (5-lap average)
10. Manor Marussia (Rossi) 1m20.623s (4-lap average)

Toro Rosso has work to do on the soft tyre, but looks strong on the medium with Carlos Sainz Jr (team-mate Max Verstappen struggled for rear grip for most of the day), while Lotus is conversely looking good on the soft tyre, but relatively weak on the medium.

Felipe Nasr's run on the medium tyre was very impressive for its length and consistency, but we don't know where Sauber stacks up on the faster tyre.

Force India looks to have some work to do overnight in order to regain its usual place at the head of the midfield (the VJM08 doesn't like riding the kerbs at all, making life more difficult for its drivers here), while McLaren-Honda and the Manor Marussias are unsurprisingly cut adrift at the back.

Fernando Alonso walked forlornly away from his MP4-30 after his Honda engine broke down in second practice, and there's no reason to feel optimistic for the rest of his weekend based on team-mate Jenson Button's running.

Perhaps both McLaren and Ferrari will be praying for rain on Saturday and Sunday, though Mercedes isn't exactly slow in the wet...