Romain Grosjean was left seeking answers from his Haas team after enduring a difficult Spanish Grand Prix on Sunday.
Grosjean started 14th in Barcelona and made the most of a frenetic start to battle his way into the top 10 early on.
However, the Frenchman slowly dropped back after a front-wing failure before ultimately retiring with 10 laps to go due to a brake issue.
Both Grosjean and teammate Esteban Gutierrez struggled all weekend long with the setup on their car, leaving the Frenchman downbeat and in need of an explanation after the race.
“I had a very good start, a very good first lap,” Grosjean said.
“I managed to get into the top 10 and was fighting there. Then my front wing decided to go, for some reason.
“We came back to the pits, fitted a new nose, got some tires, but then the brakes went. The car wasn’t having a good day.
“We really need to find out what’s going on because we reverted back on most of the setup, and we’re still very much struggling with the balance.
“Testing this week is going to be very important for us.”
Teammate Esteban Gutierrez enjoyed his best race of the season in spite of the team’s problems, finishing 11th.
“It was a very tricky weekend for us, which started with a few problems in FP2 on Friday,” Gutierrez said.
“However, the team did a great job in recovering. In the race, I was doing my best from the beginning to the end.
“I think we could have done a bit better with the tires – maybe taken a bit of a longer stint with the softs as toward the end of the race I just ran out of tires. However, it was really enjoyable out there and I had some great battles throughout.
“Today wasn’t straightforward for us to finish in the points, but we’re finding more consistency in the car, which will give us more opportunity to go forward.”