Haas boss Guenther Steiner has no answer for why his team was so off the pace at the French Grand Prix, which he labelled its worst weekend since joining the F1 grid four years ago.

Haas was slow from the get-go at Paul Ricard, with Kevin Magnussen only just scraping out of Q1. While Romain Grosjean retired before the end of the race Magnussen finished 17th, with only the two Williams cars -- which have been a distant last all year -- behind him.

The American team came into the season looking like the strongest team in the midfield but has now suffered two difficult races -- at the previous race, Magnussen said it was the worst he had ever felt in a race car. Steiner thinks things were worse in France.

"In the four-year history, I think this was our worst weekend," Steiner said. "In the race we still struggled.

"I don't know... what is bizarre to me, a car that was good enough to qualify seventh and eighth in the first race and then all of a sudden be second-last. Don't ask me what it is, I don't know. Don't ask me please because I wouldn't know.

"We need to find out, it's very disappointing, ending up in this situation but also not having an understanding of it, that's the worst of it all."

Haas struggled for pace throughout the French Grand Prix weekend. Mark Thompson/Getty Images

Steiner said France was worse than Canadian Grand Prix two weeks earlier because at the latter it had the pace on Friday and would likely had a better race had Magnussen not crashed at the end of Q2 -- not only did it force the Dane to start the race from the pit-lane in a rebuilt car, it also prevented Grosjean from progressing to the top-10 shootout in qualifying. In France the pace was never there -- after qualifying, Grosjean told the media it was time the team stopped focusing only on its problems with tyres and started accepting some of the blame for the lack of pace.

"It's a lot worse, this one," Steiner added. "Then if you think in Monte Carlo we qualified sixth and the race pace was... it's difficult to say in Monte Carlo because everyone was going slow for obvious reasons, but the race pace was there as well. So it's very bizarre, the whole thing."

When asked if there had been a depressed mood after the race, he said: "It's not depressing, I'm realistic. I'm not getting depressed.

"I'm getting... angry is the wrong word. For me it's a challenge but it's not a positive challenge -- but we need to get out of this, if you get depressed you give up. We never give up, you never give up, in racing the day you give up is the day you are nowhere. You need to get the anger out, and just keep on working. That is what I told the guys, 'You need to work a lot more now than you did before because now we are in the shit.'

"There's no point waiting for something coming up, you need to go back now and understand why we are where we are. That's the only thing you can do. And then, once you know why you are where you are, then you can find solutions."