BARCELONA (Reuters) - Jenson Button completed just one timed lap as misfiring McLaren's hopes of picking up speed in Formula One's final pre-season test stalled before lunchtime on Thursday.
Racing director Eric Bouillier had said last weekend, after Fernando Alonso crashed and was airlifted to hospital, that the team would be "pushing harder than ever" at the Circuit de Catalunya.
Pushing the troubled McLaren back into the garage turned out to be closer to the truth, though it was not what the Frenchman had in mind.
On a day when Brazilian Felipe Massa was quickest for Mercedes-powered Williams with 103 laps to his credit, McLaren's woes stood out starkly with Button's lap nearly eight seconds slower.
Sweden's Marcus Ericsson did 122 laps for Sauber, and was second fastest on the supersoft tyres, but Mercedes experienced rare power unit problems with double world champion Lewis Hamilton putting in a comparatively meager 48 laps.
Button started off with some aerodynamic runs but, with only one of seven laps producing a time, noticed a vibration that required a lengthy change of the Honda power unit and ended McLaren's presence on the track for the day.
The 2009 world champion is no stranger to such setbacks and will be back in the car on Friday before Denmark's Kevin Magnussen takes over for the final two days.
Alonso will not be back behind the wheel until first practice for the March 15 season-opener in Melbourne although even that remained in doubt.
McLaren Group head Ron Dennis told reporters that his driver, released from hospital on Wednesday after three nights under observation, was raring to go but doctors had advised rest.
"I can’t foresee any reason why not but I’m not the doctor," he said when asked whether the double world champion would be racing in Australia.
"There will be some tests, there are processes laid down within the FIA and I can’t see any reason why he won’t sail through. But it’s not for me to determine. It’s not for me to say yes or no," said Dennis.
Alonso's accident has triggered considerable speculation about what really happened, with the crash not caught on camera, and Dennis sought to dampen some of the wilder theories circulating.
"People are saying we’re concealing, we’re doing this, we’re doing that, and it’s a complete fabrication," added the boss who recognized McLaren have a mountain to climb with new engine partners Honda.
Editing by Tony Jimenez