Charles Leclerc and Carlos Sainz qualified fourth and fifth, but in Sunday’s race they tumbled down to ninth and 10th, not helped by the fact that both stopped before a safety car intervention that gave rivals a helping hand in the form of cheap stops.
However, Vasseur says that the other key issue was that the team didn’t get enough information on tyre degradation on Friday, when Charles Leclerc lost the whole of FP2 to a mechanical issue.
As a result the engineers overestimated the impact of degradation with the new Pirelli construction, which was introduced at Silverstone.
The team suffered badly with degradation earlier in the season, and it's one of the characteristics of the car that it has been working hard to address.
"Starting from P4, P5 we had the feeling after the quali that we could have done a much better job than this,” said Vasseur when asked by Motorsport.com for his verdict on the race. “We can't be happy finishing P9, P10.
“But now we need to have a deep look on the weekend, not just on the race. I think we didn't do the long stint on Friday, only the soft compound, and Charles was struck in the garage. And we were a bit scared with the deg.
“Probably somewhere in our mind we had the first races of the season, where today [Sunday] we were far too conservative on the tyre management, and we didn't push enough.
“Then we were a bit unlucky with the safety car. This is not in our hands, and we don't have to think about this, we have to think about what we can manage. And honestly, I think that we could have pushed much more."
Regarding Leclerc’s relatively early stop on lap 18, Vasseur said: "We were fighting with Russell, and we were thinking that he will pit, and we will have to fight with Russell [again].
"For sure now after the race, it's quite easy to say that we will have to extend and to push more on the tyres.
“But I think where we lost the most is not at the stage of the race, it's that when we put the hard with Charles, I think we did something like 10 or 12 laps before the safety car and he had zero deg and he could have pushed much more.
“It was a misunderstanding on the deg. This is coming from Friday, and it's not coming from the race today [Sunday]."
Vasseur acknowledged that one of the aims of recent updates was to address degradation.
"It's difficult to say when you're finishing nine and 10 that we did a good job,” he said.
“But overall, I think that it's true that we had much less deg, that was our main issue at the beginning of the season. And it was not the case today.
“Perhaps we had a lack of pace compared to the Mercedes, but not the deg. And the pace, perhaps the car is a bit unstable with the wind. We knew before that Silverstone could be a difficult one for us.
"The wind was extreme and today, it was the same as Miami, but the performance was much better than Miami. Because I think we are focused on this into the development.
“For sure the car was unstable, I don't know if it was more unstable than the others. Looks like we struggled a lot, perhaps a bit more than some others when we are into the train. But it's still a characteristic of the car.”
