Jolyon Palmer fears he and the Renault Formula 1 team might be unable to fix his oversteer problems during the Russian Grand prix weekend.
The 25-year-old described the Chinese GP two weeks ago as "maybe my worst ever as a racing driver" after battling with car problems the team has subsequently worked to identify and eliminate the cause of.
But Palmer complained of snap oversteer after ending both of Friday's free practice sessions in 18th position, 0.773 seconds slower than new Renault development driver Sergey Sirotkin in the first and 0.495s off regular team-mate Kevin Magnussen in the second.
"I have a few concerns that we are not going to be able to get on top if it," he said when asked by Autosport if he feared having to carry the problems for the rest of the weekend.
"We've done two of the three practice sessions now, we've only got an hour left and while the balance is better on the super-soft tyres, there is still the same inherent problem.
"We can mask it, but I don't think we are going to find or cure it and we need to do more work to try and understand what's going on."
Palmer is confident the problem does not lie with "something strange I'm doing" behind the wheel.
While he says there is no indication the problem lies with the car's monocoque, he said he would be interested to see what happens if the team attempted a similar chassis change to the one tried by Sauber for Felipe Nasr this weekend.
"Nobody could understand at Sauber why Felipe [struggled] as he's not a rubbish driver, but he looked very bad in the first three races," said Palmer.
"It's only Friday but it looks like he's suddenly back to what he's been able to do.
"I don't know if that's the case here, there's no indication of it but I don't think with these things you can really tell too much until it happens.
"It would be an interesting test."
Magnussen had what he described as a "similar" oversteer problem, although he conceded it might not have been as dramatic as what Palmer is struggling with.
"We have similar problems, maybe on a different level but we are complaining of the same issues," said Magnussen.
"I'm not completely sure what he has but it sounds like he's having oversteer mid-corner, maybe he has it a bit earlier, I don't know.
"It's encouraging that we are complaining about the same things so we can work in the same direction."