5 Key Takeaways from 3rd Formula 1 Test in Barcelona

Formula One's 2015 pre-season testing is over, and the teams will already be shipping personnel and parts out to Melbourne for the Australian Grand Prix.

The race takes place on March 15—less than two weeks away.

Mercedes will start as clear favourites, but behind them we'll be treated to a huge battle for second. Three teams look capable of grabbing the final spot on the podium: Williams, Ferrari and Red Bull.

Further back, it looks set to be tight as well. The likes of Toro Rosso, Lotus and Sauber will all be fighting for points and could even be joined by Force India. The Silverstone-based team had only two-and-a-half days to test the VJM08 but still managed 365 laps.

McLaren only did 380 in 12 days.

Testing is never 100 percent reliable as a gauge of how the season will go, but a vague picture of the year ahead has already emerged.

Here are five key takeaways from the final test.

Mercedes Are Massively Quicker Than Everyone Else

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Mercedes dominated 2014, and all indications are that we're due for another crushing "silverwash" this year.

Neither Lewis Hamilton nor Nico Rosberg did qualifying simulations on the supersoft tyres. Their rivals did, but the combined efforts of Williams, Ferrari and Red Bull all came to naught.

Even on the quicker compound, they couldn't match the Silver Arrows' pace on the soft tyres. Nor could they match Mercedes' lap totals—the W06 did a total of 1,340 across the three tests, a distance of 6,120.57 kilometres.

Toward the end of 2014, the gap between the quickest Mercedes and the rest of the field over a single lap was substantially less than a second. It was four-tenths of a second in Russia, eight-tenths in the United States and six-tenths in Abu Dhabi.

In the races, they had at least a second in hand when needed.

If the testing times are truly representative, they'll have around the same at the start of this season—and it's hard to see their rivals bridging that kind of gap.

Unless something goes wrong or the cars fail, Mercedes look like they have the pace to comfortably win every race.

Williams Are Podium Contenders Again

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We all knew Williams were hiding their true pace throughout the first and second tests, concentrating on their own programme. As expected, they showed their hand at the third and final test—and look more than capable of fighting for frequent podiums again in 2015.

Reliability was good thanks to a strong Mercedes power train, and the team's performance on the time sheets was good as well.

Valtteri Bottas set their quickest lap—one minute, 23.063 seconds—using the supersoft tyres. This was faster than anyone bar Mercedes. Per James Allen and Dominic Harlow, Williams are also good over a race distance.

A day spent on pit-stop practice during the second test won't have done the operational side of the team any harm, and speed-trap data reported by Grand Prix 247—albeit from the second test—shows that the FW37 has retained the useful, low-drag characteristics of its predecessor.

Williams came in third in the 2014 Constructors' Championship. There's no reason they can't aim for second in 2015.

But They Face a Titanic Battle for 2nd

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Williams are one of the podium contenders, but they face a real fight to be second best.

Ferrari carried their strong form from the first two tests into the last. Their single-lap pace was much improved from last season—Kimi Raikkonen put in their best with a 1:23.276.

The lap was two-tenths shy of Williams' fastest on the same supersoft tyres, but at the last race—2014's Abu Dhabi Grand Prix—he was over a second slower in qualifying. Not only does the car look quicker, but it also looks to have speed that the notoriously setup-sensitive Raikkonen can use.

Sebastian Vettel, expected to be the de facto leader at Ferrari, was slower—so it's likely that the SF15-T has even more pace than we saw.

Red Bull will be the third piece of the jigsaw. Our analysis is hampered slightly because they didn't do a qualifying simulation at the third test, but the RB11 looked reasonable in race trim.

BBC Sport's Andrew Benson reports the team's race simulations were broadly similar to those of Williams.

So fans more interested in multiteam battles can at least take some solace. Even if the fight for the lead will be very much a two-horse affair, it's extremely tight between the three closest challengers.

And when McLaren—whose car looks good in spite of multiple reliability problems and whose driver lineup is perhaps the strongest on the grid—can get their power unit running at full whack, it may become a four-way tussle.

Force India Are Either Very Lucky or Very Clever

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Things weren't looking good for Force India before the third test. They had yet to debut their 2015 car and would have only three days—it wasn't due to be ready until Day 2—to iron out teething troubles.

Fortunately, there weren't many of those. Though it missed almost all of Friday morning, the car was reliable straight out of the box. In just two-and-a-half days of running, Force India clocked up 365 laps of the Circuit de Catalunya.

That's only 15 fewer than McLaren managed in 12 days.

There wasn't enough time to look at much in the way of setup work, which driver Sergio Perez spoke to reporters about in Spain, per ESPN:

"

I'm always excited to find out about a new car. It was so good we had a reference with the old car. We are a couple of steps behind our competition, we only had two days but it's a reality, we can't hide it. But it's a promising start. I think it will take us a couple of races to get to where we want to be.

But the most important thing and something that makes me feel a bit more comfortable is that we have a very clear direction on where we need to improve the car and the steps we have to make as a team to improve the car. That makes me a bit more comfortable but there's a lot of work ahead of us and as I say we are a couple of steps behind the competition.

"

While not quite ready to be competitive, Force India aren't far away—quite an achievement for a team that did less than three days of testing.

The Midfield Is Still the Midfield

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Much of the attention during the test focused on the bigger teams: Mercedes were doing this, Red Bull were doing that and Ferrari were somewhere in the middle.

But the smaller teams were there, too, and this is usually the stage where we identify whether any of them have taken a significant step forward. From what we saw, they haven't.

Lotus, Toro Rosso and Sauber all did impressive-looking times on the supersofts, but none got within a second of the times Mercedes did on soft tyres.

The gap back from Williams' supersoft times was around a second. Looking at some qualifying times from last season, that's an improvement—for example, Sauber were around a second-and-a-half shy of Williams at the 2014 United States Grand Prix (Adrian Sutil Q2 versus Valtteri Bottas Q3).

But the gap is still there, and it's still significant enough to keep those smaller teams very much in the middle of the pack—or, if Manor don't make it, at the rear.

All lap-time and -count data used throughout sourced from Formula1.com unless otherwise stated.