The F1 team that's had the best winter

As F1 launch season approaches, the inevitable demand for teams to nail their colours to the mast and declare their ambitious targets for the season ahead begins.

For them to do so with any sense of certainty is nigh on impossible, though, for a team's form is always as much about what its rivals do as what it achieves itself.

You can produce a new car that's one second a lap quicker than its predecessor, but if your opposition have all found two seconds over the winter then you are going backwards.

Mercedes could extend its advantage over the rest this season © LAT

Likewise, if you find just half a second but your rivals have failed to unlock any more speed, then you've actually made progress.

It's the same story on the engine front. Renault and Ferrari may well feel that the winter is a triumph if they can unlock around 70bhp, but it will count for nothing if Mercedes has managed to unleash even more than that.

This is why the build-up to the first test is simply a time for guessing. Teams will have some idea about the things they can control themselves, but will have very little knowledge about where it leaves them in the overall pecking order.

What you can plot at this time of year, however, are trends, for F1 is very much a sport where success is a long game. There is an inevitable cycle of progress and decline. Some teams achieve higher peaks than others, and some are unable to maintain their best form for very long. The aim, of course, is to ensure that your peak lasts as long as possible.

This ebb and flow of progress and decay is influenced by multiple factors, be it personnel joining or departing, a technical advantage, or simply staff that gel perfectly.

Minimising the negative factors and maximising the positives is, of course, the best way to ensure that you keep moving forward. And if you wanted to single out any team that's done just that over the past few months, then it's Williams.

It is one of the few teams that has enjoyed a winter of pretty good stability, and any major staff changes have happened for positive reasons to bolster the organisation rather than as a response to failures.

This is in stark contrast to what's happened elsewhere. Red Bull is without Adrian Newey's full attention; Ferrari is undergoing a major restructure; and even Mercedes has lost key figures like Bob Bell and Jock Clear.

On the technical front, things also look promising. There is no change of engine partner like McLaren is going through, and nothing to suggest that its Mercedes advantage won't remain.

Having the same power unit as the world champion team is a great thing, for Williams has no reason to worry about any major progress that comes out of the Mercedes engine headquarters at Brixworth.

Indeed, while some insiders have said Mercedes' rivals should brace themselves for a shock about just how much of a step forward its 2015 power unit will deliver, Williams's response will be different. Bring it on, it will say.

But perhaps best of all for Williams, when we look for trends, is the fact that it showed clear progress last season; it became stronger - more confident in its own abilities - as the campaign wore on.

Nothing is guaranteed in F1, and the big budgets of Red Bull, Ferrari and McLaren will all help fast-track their recovery. But Grove has solid grounds for optimism in 2015.

Williams chief technical officer Pat Symonds certainly carried with him a sense of ease about the work being done when I spoke to him last weekend, although he was well aware that success this year is not just down to his team's efforts.

Symonds appears in confident mood ahead of pre-season testing © LAT

"We were probably fortunate that some of our rivals had problems last year, but let's not take anything away from what we achieved as well," he said.

"Yes we had a great power unit. But equally in 2013 we had the same power unit as the guys that won the constructors' championship, so I think we have moved on a lot.

"We are fighting with the big boys now though - the guys who are spending twice as much money as us - and that makes it very, very difficult to go forward.

"But if we fully acknowledge all the things that brought us success in 2014, if we make sure we consolidate those, make sure we fully understand and incrementally move forward in all of those areas, then we can at least maintain if not improve where we are."

And maybe, just maybe, Williams could do even better than that. Challenge Mercedes outright, perhaps?

Just don't expect any firm answers on what is possible just yet.