Sainz's car suffered severe damage after running over a water valve cover early in the opening session of practice.
The team had to rebuild the car around the spare chassis, and also swap the power unit and gearbox.
Unfortunately for the Spaniard, one of the damaged items was the energy store, and by taking a third example for the season he automatically triggered a grid penalty.
Vasseur tried to argue with the stewards that it was a case of force majeure but to no avail.
"Sure, I went there, and I discussed with them," he said when asked if he'd tried to get dispensation. "It's a strange feeling for us, because first, I don't think that we did something wrong.
"We have to pay a mega price for this. And on the top, you have the penalty when you know that we are fighting for the championship, and 10 places is a huge hit.
"OK, we that we have to try to avoid thinking about it, to do the job that we can come back. We have a good pace, we have to be focused on the quali, and then to do a good race. We don't have time to discuss this."
Asked if the other teams could have supported his case, he said: "I don't think that it could be a decision from the teams, to say that we allow them to do this or that. Now tomorrow if someone pushed in the other direction, it's another story."
Source: Autosport