Jenson Button admitted he still had not 'found his feet' with McLaren's Singapore setup.
The Briton was half a second off his pole-winning team-mate Lewis Hamilton's pace as he qualified fourth for Sunday's race - and conceded he currently looks unlikely to fight for victory.
"I found it tough," Button said. "I am struggling, not finding my feet with the car, and with my timed lap with the rear going away quite quickly."
He said that unless the car felt more comfortable in race conditions, a win was out of the question.
"You can hope for a win from there but the pace wasn't there in qualifying for me so I hope the car is better in the race," Button said.
Hamilton has shown strong form all weekend, which Button said showed the difference between finding an ideal setup for the tires and circuit conditions, and not being fully comfortable.
"I think Lewis has found a good setup and it works for him but for me it is not so good," said Button. "I think you can see that through [Pastor] Maldonado. I think they have got it together and you wouldn't expect them to be so quick. If you get the right balance for the tire you can be quick.
"I think it is very tricky as we have high degradation on the super-soft but on the soft it is much more consistent. What is funny is that we are not wearing out the tire quickly, we are just losing grip."