Formula One world champion driver Jenson Button has made his McLaren debut on the test track, but says it's too early to tell whether the car is good enough to take him to a second title.
The Briton was fifth fastest of the seven drivers who took to the track on the last day of the first pre-season test, and completed 82 laps in the MP4-25.
Button says it was a long day and it would have been nice to get more testing done.
He says he's already had to change a lot within the car, after initially feeling too high and uncomfortable in the drivers seat, but is happy with the improvements.
Fernando Alonso clocked the fastest time on the final day of testing for Ferrari, ahead of the Sauba of fellow Spaniard Pedro de la Rosa in second and the Mercedes of Michael Schumacher in third.
