Sergey Sirotkin felt it was 'impossible' to keep up with the midfield during the Canadian Grand Prix as Williams continued to struggle with the inconsistent FW41.
After making a good start to the race, the Russian was up to thirteenth place as the safety car came out for the crash between team-mate Lance Stroll and the Toro Rosso of Brendon Hartley at Turn 5.
As the race restarted he quickly fell back through the pack and was unable to match the pace of his rivals in front, eventually dropping to the back of the pack trying to fend off the Sauber of Marcus Ericsson.
"It was a difficult race, said Sirotkin. "The start was particularly tough in the beginning with the prime tyres compared to the much softer compounds of everybody else. Still, I was able to gain some positions at the start.
"However, with the safety car and an extremely poor warm up with the harder compound of tyre, it was impossible to keep up with the pace. We were the slowest car of the day and we have done our best to finish the race despite the issues we’ve had.
"That’s where we are and we have to be honest with that."
Despite an earlier pitstop in order to try and maintain track position with the purple-marked Ultrasoft tyre, chief technical officer Paddy Lowe admits Sirotkin was unable to extract any extra pace from the softer tyre and the team will be looking further into the problems they suffered in Montreal.
"On Sergey's side, due to the harder tyre slow warm up, he lost the positions he had gained at the start after the safety car," Lowe added.
"He then settled down to protecting a position ahead of Ericsson and Vandoorne. We chose a relatively early stop for the ultrasoft to go to the end, thinking that this would gain an advantage, but unfortunately, we didn't find any pace in these softer tyres, which appeared slower than the Supersofts.
"We know we are not where we need to be and we have a lot of work to do. We are working very hard behind the scenes and intend to come back stronger as soon as we can."
Another non-score for Williams keeps them at the foot of the Constructors' Championship with just four points.
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