Downcast Robert Kubica rues 'lost' day as Williams curtails F1 test

The team had to curtail its running on Friday due to the amount of wear and tear on components on the FW42.

It had already missed the first two and half days of testing due to the car's late arrival, before seeming to recover with some significant mileage in the second week.

But while Kubica posted his fastest lap of the pre-season with a 1m18.993s on Friday, he was left clearly dissatisfied with how his Friday had unfolded.

"We lost another day today," Kubica said. "Of course we did some laps, but the car's state was far from optimal.

"We had some issues. Unfortunately the car was not representative to what it should be, and this had a big impact on our test, our running programme of today.

"All the information was misleading and in some way also it was difficult to get any information for Australia."

Kubica said that the unproductive final day stemmed from a lack of spare parts, which came as a result of the initial delay of the FW42.

"Of course we faced a big delay, and some of today's issues are a consequence of being in a rush," he said.

"If you struggle to have a car for the week before, you struggle to have spare parts.

"And unfortunately today it was required to have bits to replace, and we couldn't replace them.

"In the end we did the maximum from what we have, but this maximum is not enough, because in the end the car was from optimal."

Williams technical chief Paddy Lowe admitted Kubica could not do a long run because the team was simply out of parts to replace on its test car.

"The long running in the afternoon was unfortunately brought to a halt because a number of critical bodywork parts had reached a stage of degradation that meant that we were no longer learning useful information from the car nor indeed for Robert," he said.

"So we decided to switch our time to those final race procedural practices (starts, pitstops etc) that we need to do before Australia.

"Having arrived late to the testing, our reliability during the running itself has been incredibly high. Up until today we were on track to complete our originally intended mileage and to consume all available tyre sets.

"But today this car has become ultimately too tired to continue.

"In the interest of saving our resources for the important racing in Australia we felt it was right to change the plan."

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Kubica's fastest lap was over seven tenths slower than what team-mate George Russell had managed on Thursday, and nearly 2.8s down on Sebastian Vettel's benchmark time for Ferrari.

"In general, the car is not as its best and this has affected our performance most particularly this morning with Robert in the qualifying simulation and to some extent with George yesterday," Lowe added.