If Hamilton does start well and notches up a number of early wins, it risks making the title fight a one-horse race. That is not good for Liberty Media, F1 or Bottas
Formula One 2018 success hinges on Valtteri Bottas' ability to beat Mercedes-GP teammate Lewis Hamilton
There is always intrigue surrounding Formula One pre-season testing.
Just because a driver is quick does not necessarily mean they are really fast as only they and their team know how much fuel they are running in the car.
The confident teams do not usually chase lap times, because, well, what is the point? If a team has a strong package it is not always advantageous to highlight that to rivals. The earlier they know how fast another team is, the sooner they can try to find more speed in their own car.
This is not to say that Ferrari, who were fastest in testing in Barcelona over the winter, are not going to be competitive. But the fact that expected midfield battlers McLaren, Renault, Haas and Toro Rosso were all faster than defending champions Mercedes-GP can be taken three ways.
First, those teams have improved considerably. Second, Mercedes are in trouble. Or third, and the more likely scenario, the German marque are very confident with their car.
The F1 W09 has looked impressive without setting a sensational lap time, and covered the most laps over the two tests in Barcelona at 1,040 to demonstrate good reliability.
Mercedes were comparably quick to Ferrari and Red Bull Racing, their expected main rivals, on the harder Pirelli compounds, and their confidence was such they did not show what pace they were capable of on the softest, and quickest, tyre available, the Ultrasoft.
It is not unreasonable, given their dominance of F1 since 2014, during which time they have won the drivers' and constructors' double the past four years and have won 63 of 79 races, that Mercedes are set for another year of success.
If that is the case then arguably the most important driver this F1 season could well be Valtteri Bottas.
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With new F1 owners Liberty Media starting their second full year in charge, they need an entertaining product on the track to back up their strong marketing as they attempt to garner new interest in the sport.
Lewis Hamilton won the 2017 title with two races to spare, but that did not tell the full story of a season where Ferrari pushed him and Mercedes hard. Hamilton proved comfortably quicker over the year than teammate Bottas and that could be a factor if Mercedes start the season with a speed advantage over the rest of the field.
Bottas did end the season on a high by winning the Etihad Airways Abu Dhabi Grand Prix in November, but Hamilton's happy demeanour post-race spoke of a man content with a rare loss to the Finn, given his fourth drivers' title had already been won.
The final points total in 2017 between Hamilton and Bottas was 363-305 in the Briton's favour, and he had nine wins to the Finn's three.
There were weekends, such as Russia, Monaco, Austria, Hungary and Abu Dhabi where Bottas was a match, or even quicker, than Hamilton. But five races over a season is not enough to win a championship against Hamilton, and Bottas must step up his consistency in 2018 if he is to be a genuine challenger.
If Mercedes do have a speed edge over the rest of the field, it is crucial to Bottas, and to those hoping for a close fight for the No 1 spot, that he starts the season well, beginning with Sunday's Australian Grand Prix.
Bottas has talked a good game in pre-season, saying he believes he can fight for the title, but the proof must come on the track. Abu Dhabi was a great effort, but the championship was done and dusted.
He must show from Melbourne onwards he is capable of taking the fight to Hamilton and unsettling his teammate.
That was what his predecessor Nico Rosberg, the 2016 world champion, did so well. He was not as fast as Hamilton overall, but could beat him on certain days when things went for him, and was close enough to capitalise on any problems.
If Hamilton starts well and notches up a number of early wins, it risks making the title fight a one-horse race. That is not good for any of Liberty Media, F1 or Bottas.
The pressure is on the Finn to show he has what it takes to be a championship challenger, and if he is capable or it or not will be a fascinating narrative of the coming year's action.