It's not often that an in-season test in Bahrain offers any insight into the best drivers in the world, but this week might have done just that.

On Sunday after his victory in the Bahrain Grand Prix, Sebastian Vettel was asked if he would be testing this week, to which he replied "yes", and was then asked: "You're relentless aren't you?"

"Well, I thought halfway through the race that I'm already really looking forward [to the] next time [I] jump in the car, which is in two days. So I'm looking forward to it," Vettel replied.

Leaving aside the fact he was already driving the Ferrari at the time (stop wishing your life away, Seb), the response highlights Vettel's determination to make the most of every opportunity to improve himself as a driver. Not only was he testing, he was the only driver to be in the car on both days, as he carried out duties for Pirelli on Tuesday before switching to the main Ferrari seat the following day.

Vettel is known to be a perfectionist, looking for every possible advantage when the opportunity to win presents itself. He was the only driver to visit Pirelli's factory ahead of one of his title-winning years at Red Bull, and also carried out the highest number of tire testing laps of the leading drivers in 2016. Should it be any surprise that he has started the year so strongly?

Well, Lewis Hamilton is certainly sitting up and taking notice. Traditionally, Hamilton does not like to test – he still maintains he was better off barely running the tires during their development last season – but he, too, was present in Bahrain this week. Even if he was possibly somewhat reluctant (and understandably so, as the test came immediately following back-to-back races) Hamilton completed a full day in the desert heat to aid the Mercedes program.

Perhaps more so since last year's intra-team battle for the championship, Hamilton has a lot of power over Mercedes. But the team made clear the importance of having race drivers carrying out this week's testing and the three-time world champion delivered what was required, fully aware of the close battle he is facing for the title this year from a man with one crown more on his racing resume.

While he has always been supremely confident in his own ability, Hamilton has also been able to gauge just how good Vettel is in a close fight over the past three races. The Mercedes and Ferrari are similarly matched in terms of outright race pace, with the Mercedes the slightly quicker car one lap, but Vettel has shown he is capable of capitalizing on every chance he is given.

"It's small percentages now, which I think is what racing should be about," Hamilton said after finishing second to the German on Sunday. "We want to be operating in the top end of those, and not having 1 percent divide the win, not doing a good enough job by 1 percent and losing the race, but ultimately I think that's what it's going to be about this year.

"I think that's exciting and I think all of us – and I speak for all of us in that team – need to be operating at our maximum, week in and week out."

Both drivers have already spoken of their excitement at being able to race each other in relatively equal machinery, but the beauty of the battle is the fear of the unknown. Hamilton knew everything about his previous championship rival over the past three years as he fought Nico Rosberg for the title. Shared data, knowledge of the machinery and insight within the team ensured there were very few secrets between the pair, but that is not the case this year.

Mercedes versus Ferrari means there are plenty of unknown variables. Neither team knows fully what the other is doing, what its strategy is and what its full potential is each weekend. Hamilton and Vettel are going to be driven by the concern that the other man is hiding something, or taking a different approach that has yet to be seen.

As it stands the only inequality revolves around their respective teammates. Bottas performed well in Australia and showed his ability with pole position in Bahrain, although Hamilton retains the upper hand and has yet to be outscored by the Finn. Vettel, by contrast, has been far and away the standout driver at Ferrari and it's almost impossible to foresee a scenario where Kimi Raikkonen will fight back to become the team's best chance at winning the championship.

In such a situation, Hamilton may need to bank on Bottas playing the support role in order to fight Vettel on a level playing field, rather than risk losing further points as a result of being beaten more often by his teammate than his main opponent is.

When Vettel went toe-to-toe with Fernando Alonso for the 2012 championship, there wasn't the same level of respect as that enjoyed between the rivals this year. Alonso rightly felt the Red Bull was the superior car, but that wrongly led him to belittle Vettel's ability. Hamilton clearly respects the four-time world champion's quality, and believes it is a mutual feeling that will endure – and perhaps even be strengthened by – the intensity of this year's battle.

"I honestly think it will stay the way it is," Hamilton said after coming out on top in China. "Of course we'll be in that scenario where one of us thinks something is unfair, being too aggressive, whatever it may be.

"I honestly think we've come a long old way, we've experienced a lot and we respect one another. Amazing sportsmanship you know, he enjoys it and also acknowledges the person next door, and we'll do the same thing. I think that's a great synergy to have.

"Naturally he wants to beat me, and vice-versa. As I said, he's performing at his best, he's rapid out there. When I'm able to get ahead, it only compliments you, and vice-versa."

The V6 turbo era has been crying out for a proper inter-team fight, with 2012 the last time you would genuinely claim the title contenders would come from more than one team. Since then, both of this year's main candidates have added a pair of titles each as they cement their places as greats of the sport.

This year, Hamilton and Vettel each have an adversary worthy of the other, pushing them to new heights and demanding they deliver their best or face defeat. Now we get to sit back and enjoy the show.