The mysteries emerging at the US GP

It's fatuous to talk about the chances of Sebastian Vettel striking back in the title race given it's surely now a question of when, not if, Lewis Hamilton clinches the crown. Besides, the Mercedes driver was fastest on Friday, so it's going to be another easy win for Hamilton, right?

Well, perhaps not, because there was a hidden battle going on under the surface of a mysterious day of practice for the United States Grand Prix. Anyone who thinks it's a done deal has jumped the gun for a multitude of reasons.

"Ferrari had a bit of a troubled day today, so maybe we haven't yet really seen where the opposition are at," said Mercedes technical director James Allison after the day's running at Austin was concluded. And he's probably right.

That's why the Silver Arrows can't be too over-confident even after a strong first day, for Hamilton's car at least. It was certainly a promising start for Mercedes, but it has unquestionably shown closer to its maximum potential than Ferrari.

Hamilton's supremacy is undeniable on raw pace - at least prior to the changes all teams will make overnight. As with all analysis of Friday practice, it's a snapshot of a team's weekend-in-progress, with how the data is absorbed and acted on key to what happens in qualifying and the race.

The data that mattered is that Hamilton was the only driver to dip under the 1m35s barrier, lapping 0.331s below his 2016 pole position time. He was four-tenths quicker than next-best.

Pure pace ranking

1. Mercedes (Hamilton) 1m34.668s
2. Red Bull (Verstappen) 1m35.065s
3. Ferrari (Vettel) 1m35.192s
4. McLaren (Alonso) 1m36.304s
5. Williams (Massa) 1m36.460s
6. Force India (Perez) 1m36.481s
7. Renault (Sainz) 1m36.529s
8. Toro Rosso (Kvyat) 1m36.761s
9. Haas (Magnussen) 1m37.285s
10. Sauber (Wehrlein) 1m38.165s

It's no great surprise to see Hamilton lapping so quickly. He's a master of the tricky Austin circuit, with its blend of high-speed sequences and more technical corners, cambers and troubling bumps. It's not an easy track for braking either, another area where he excels.

It's not a straightforward track to master, you only need look at some of the yawning chasms between team-mates for proof of that. But there's no doubt Hamilton is extremely strong around this varied and challenging circuit.

The gap of six-tenths back to team-mate Valtteri Bottas is in line with what we've seen in recent times, suggesting this was a fairly accurate read of the speed of the car. Bottas continued to complain about having more set-up work to do, suggesting there will be no reverse of the pattern seen for the second half of the year at Mercedes.

Vettel's deficit is more concerning. He was behind the Red Bull of Verstappen, by just over a tenth, but he claimed at the end of the day that it was not necessarily representative.

"When we're on track, I think yes," said Vettel of Ferrari's prospects of taking on Mercedes on pace after a difficult day.

"But today we spent more time in the garage which wasn't the right thing. But sometimes it's like this. I said to the guys, we have a good car. The lap I had was the only real lap I had. And it was not very good. I'm sure we can step it up."

Verstappen's pace hinted Red Bull could at worst be close enough to capitalise on any underachievement from those ahead and might perhaps even be able to be a threat on race pace.

You could certainly make a case for Ferrari being in the game based on very limited information

But there remains the possibility that Verstappen could be hit with a grid penalty should he switch to the latest R.E.17G Renault engine that has already been fitted to the Renault of Nico Hulkenberg and the Toro Rosso of Brendon Hartley.

Perhaps the clearest sign of how strong Red Bull thinks it could be at Austin will be whether it decides not to put the new engine in to keep Verstappen up at the sharp end.

With Vettel not able to do any long runs and managing only 11 laps in total after his first-run spin and problems with a "jelly"-like front axle, it was left to Raikkonen to fly the Prancing Horse flag on the long runs.

Looking at ultra-soft pace, he didn't give us much with just three laps to compare against the other ultra-soft runners who all posted at least four relevant laps. To be generous to Ferrari, Raikkonen's average is taken over only two laps - excluding the 1m41.258s he did between his faster laps of 1m40.353s and 1m40.842s.

This at least puts Ferrari closer to Mercedes, albeit now behind pacesetter Red Bull, with the caveat that this is based on Bottas's pace, which was actually quicker than Hamilton's.

Long run ranking

1. Red Bull (Verstappen) 1m40.172s
2. Mercedes (Bottas) 1m40.226s
3. Ferrari (Raikkonen) 1m40.598s
4. Force India (Perez) 1m41.104s
5. Williams (Massa) 1m41.623s
6. Haas (Grosjean) 1m41.753s
7. McLaren (Vandoorne) 1m41.811s
8. Toro Rosso (Kvyat) 1m42.158s

Only eight cars are listed as neither Renault nor Sauber offered any meaningful long-run data on the ultra-soft tyres.

Ferrari's pace is impossible to infer even vaguely from this. The car is certainly not far off, and Raikkonen's brief run on super-softs at the end of the session looked decent at an average of 1m40.781s.

You'd expect a bigger gap, so Ferrari's long-run pace is surely quicker. Chances are, Vettel would have been faster than Raikkonen on the long runs had, so you could certainly make a case for Ferrari being in the game based on that very limited information.

But then again, Hamilton late on was lapping at an average of 1m40.143s on the softs - on which he is often prodigiously rapid. So with every positive that you offer for Ferrari, there's a counter from Mercedes. Especially as long-run pace isn't always its strong suit.

"Normally we're quick in practice, then when we get to race pace we're often behind the Red Bulls and the Ferraris," said Hamilton. "But today I believe we were equal with the Red Bull, so that's a positive. That's better than normal."

The other reason to imagine that the real story is hidden is the pattern in recent times. Ferrari had the pace to win in Singapore, it had the pace to win in Malaysia and it might well have had the race pace to win in Japan given track position.

Had Vettel made the start he did at Suzuka with all the cylinders on his side, maybe he would have had that. What that history all means is that Ferrari would be expected to be at the kind of level Mercedes is, at the very least on long-run pace, which again supports the idea that there's a little more in the tank for the red corner.

Further back, there's fewer surprises. But don't be fooled by the modest long-run pace of McLaren, as had Fernando Alonso done a representative run he'd very likely have been ahead of the Williams pace, and possibly the Force India too.

So what did we learn from Friday at Austin? Hamilton is fast here, but we knew that. He would certainly take some beating to be denied a record-setting sixth United States GP victory.

We also saw Ferrari perhaps shooting itself in the foot, or at least in the toe, with Vettel's error and the later axle problem. But what we can be sure of is that the run of problems at Maranello, which stretches back to the start of the Singapore GP, can't go on forever.

There's no doubt there is far more to come from Ferrari than from Mercedes

After another troubled day, perhaps the hidden pace of Ferrari could finally be turned into tangible results? And with Vettel possibly benefitting from a change of chassis for the rest of the weekend (only possibly because the team couldn't find a specific problem but wanted to cover all bases by eliminating an issue that might have been undetected) as a result of the aforementioned jelly-like characteristics of the front end, the picture could change dramatically.

Add to that the fact that today's running was compromised by the damp start to the morning session, which will have had a small impact on the run plans of all the teams, and the fact that the track will continue to evolve if the rain doesn't return (and that's a big if, judging by the ever-changing forecasts) and you have an even muddier picture.

"It's difficult to say, because Sebastian didn't really get much running," said Hamilton, who suggested that Red Bull looked like the biggest threat on Friday. But the implication is clear - Ferrari is an unknown quantity, and the one that offers the biggest concern given he was happy with his long-run pace relative to that of Red Bull.

Whatever happens, Ferrari and Vettel will need to be at their best to beat Hamilton. But strong as Mercedes looks, it's not won yet. There's no doubt there is far more to come from Ferrari than from Mercedes.

The question that Friday did not answer is just how much. Will it be enough? What we can be certain of is that things won't necessarily be as easy for Hamilton and Mercedes as a quick glance at the timing sheets would suggest as the mysteries of Friday unravel over the rest of the weekend.