Ferrari's Sebastian Vettel outgunned reigning world champion Lewis Hamilton to post the fastest time as the 2016 Formula One pre-season got underway with the first test here.
The Italian giants are expected to pose an even stronger challenge to Hamilton's Mercedes this season after Vettel showed signs of a Ferrari revival by winning three races last year. The four-time former world champion was nearly half a second faster than Hamilton in a time of 1min 24.939sec.
"It is better than being last but (being fastest) is not really important," said Vettel.
"We were happy with the car and how it felt, but it is better to be first in about a month's time."
However, after dominating the sport for the past two seasons, Mercedes's reliability sent another warning shot to the rest of the paddock as Hamilton racked up a huge mileage of 155 laps -- nearly twice as much as anyone else.
History also favours Hamilton and Mercedes. Ferrari posted the quickest time on day one of testing in each of the last two years, whilst Mercedes clocked up the laps before moving up a gear closer to the start of the season.
"I'm certain this is the most impressive first day (of testing) I've ever had," said Hamilton.
"To not have any problems on the first day is a great sign of how united and focused everyone on this team is.
"It gets harder and harder to improve, but that is why I am so encouraged today to see that the car is better and the performance we've had today."
Seven more days of testing remain at the Circuit de Cataluyna track before racing gets underway for real at the Australian Grand Prix on March 20.
Red Bull and Williams showed early signs of what could be a battle for the best of the rest as Daniel Ricciardo edged out Valtteri Bottas for third fastest.
Mclaren-Honda made a significant improvement on their disastrous performances in testing last season which set up a hugely disappointing return season to the sport for the Japanese manufacturer.
Despite a few early teething problems which frustrated race director Eric Boullier, Jenson Button was able to log 82 laps, but the MP4-31 was still well down on pace nearly two seconds behind Vettel in fifth fastest.
"We completed five more laps today than we did in the first four days of testing last year, which is definitely an improvement," said Button.
"As long as we can see improvements, and the feeling of the car is good, it's something to build on."
Unsurprisingly, newcomers Haas, the first American owned team in Formula One for 30 years, Renault on their return as a constructor and Manor Racing struggled most, although the three combined for over 100 laps on an uncharacteristically trouble-free first day of the season.
