Just four days of pre-season testing remain before the Australian Grand Prix in Melbourne on March 16, and several key themes are developing.

The first is the impressive pace and reliability of the Mercedes, with Nico Rosberg behind the wheel the W05 sompleted a qualifying simulation on Saturday setting a time less than a second slower than his pole position time of 2013.

That time was not only a full second clear of his team-mate Lewis Hamilton, but it was also 1.7 seconds faster than the next fastest time set by Kevin Magnussen and Jenson Button in the McLaren.

Finally it emerged the German completed that lap on the soft compound tyre rather than the super-soft some teams, including McLaren, had used at the Middle East circuit.

The next story was at the opposite end of the spectrum as Red Bull and Renault’s woes continue leaving world champion Sebastian Vettel and Daniel Ricciardo trailing behind all their rivals.

The RB10 turned just 106 laps over the four days at Sakhir with a best time a colossal seven seconds off the pace set by Rosberg.

“The challenge is to improve the rate of progress,” engine supplier Renault’s Rob White said, “because the gap to where we wanted to be at this stage remains substantial.”

Perhaps even more worrying for Red Bull is the deadline set by the FIA to freeze initial development of the new V6 unit is Friday, White added the French manufacturer is “weeks” behind it’s rivals.

The current champions concerns are deepened by the fact Lotus, a team who only began testing proper last week, already appears to be ahead of them while Caterham are also completing good mileage albeit by turning the new motor down.

“I think we could be the lead Renault team,” Lotus technical boss Nick Chester said.

Interestingly of the four French powered outfits, Lotus is the only one not to run a Red Bull gearbox.

All the Renault teams however are likely not going to be in the same league come Melbourne where most can only see one winner.

“The strongest teams out there are the Mercedes-powered teams,” Mercedes’ Paddy Lowe told Sky.

“The Ferrari is also looking strong, so those are the people we are watching and trying to measure against.”

Of the Italian marque, Kimi Raikkonen may have ended the second test in the barrier after crashing at turn four, but the Finn perhaps heaped his equivalent of praise on his new car claiming it was “not bad”.

The Mercedes powered teams have gone well here,” he admitted, “but we were doing our own programme. It won’t get serious until Melbourne.

“The reliability of our car has been ok,” Raikkonen is quoted by Finland’s Turun Sanomat, “but in terms of speed I do not know what’s going on.”

After a tumultuous 2013, many are pleased to see McLaren apparently rebounding with it’s MP4-29 near the top of the timings throughout all of pre-season testing.

Indeed their lead driver Jenson Button is sounding more positive when summarising his team’s test in Bahrain.

“We’re in a reasonable position but you would also like to be faster.

“We know we don’t have the fastest car,” he is quoted by Auto Motor und Sport, “but we also know that we are not slow.”

Instead the 2009 champion conceded few can likely challenge the Silver Arrows come Melbourne.

“I already have a good idea of who will be on pole in Melbourne,” he said, “but you couldn’t say who will win the championship.”

And on that final point few people are expecting a fifth straight title from Red Bull.

But Mercedes’ Rosberg insisted: “It doesn’t mean they won’t recover. What it does mean is that (Red Bull) winning again this year is likely to be a far bigger challenge than the previous four.”

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