Fernando Alonso has conceded McLaren's "disappointing" start to winter testing means they are already playing catch-up in 2017.
For the second time in three years since their reunion with Honda, McLaren endured a problem-filled start to testing with their new car.
Alonso completed only 29 laps at Barcelona, the fewest of any driver, after an oil system problem which struck on the opening installation lap kept the MCL32 in the garage until mid-afternoon.
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Although Alonso returned to the track intermittently in the day's closing two hours, the Spaniard said the team were running "very conservative" settings in order to check the car and be able to complete some running.
"It's definitely not the perfect start of winter testing," he told reporters after finishing 10th fastest out of 11 drivers.
"In terms of the performance point of view we have to concentrate and try to recover the time. We are disappointed, we are sad to arrive to the first day and not be able to run.
"We are aware of the time we lost today, we have four days for each driver before the World Championship starts and now one day is gone. So I have three days to prepare a World Championship, so it's not an ideal situation but it's the way it is. There is nothing more we can do from today more than learn from whatever happened to the car and try to recover the time in the next days."
The Spaniard and new team-mate Stoffel Vandoorne are scheduled to drive four days apiece in the car over the eight days of testing. Alonso said he would not ask the team to give him extra time in the MCL32, but suggested they would have to see how the rest of the week developed.
And although he said he had too much experience to overreact the results of one day of testing, he admitted the team had lost crucial time.
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"It's the first day of testing, so you are not too worried or too excited," added Alonso. "Even if you are in a very good position or very good position, there is a very long way to go.
"But as I said, (I am) disappointed. You have been working for three months on your physical fitness, on your simulator, on your sponsor commitments, launching the car - I think everyone did an amazing job on this car for many, many months. Now you hit the track and go on the installation lap and something breaks down and you lose the day.
"The time is very important this year with the new regulations, the new tyres."
Alonso added he was not yet in a position to judge either the MCL32 or the redesigned Honda engine, although did express optimism that F1's new breed of faster cars had brought the thrill factor back to driving he has long claimed has been missing.
"The only conclusion is the cars look nice," he said. "They are definitely faster in the corners so it's good to come back to that feeling of the downforce and be able to push the car to the limit a little bit more, so I'm happy with that.
"I saw some other cars running alongside on the track and they look very, very good.
"So I'm happy for that, happy for the sport to go in the right direction, and (F1 should) probably apologise to the fans for the last five or six years when they saw horrible cars."
The Sky Sports F1 Digital team will be providing live commentary from dawn until dusk for all days of winter testing while Sky Sports News HQ will also deliver live updates from trackside.