Lando Norris has admitted McLaren could lose up to eight tenths of a second per lap in just one area at the Belgian GP.
Both McLaren drivers have opted to use a high-downforce setup at Spa-Francorchamps to make them better in wet conditions.
It worked for Oscar Piastri, who came home in second in the sprint, but with dry weather expected for Sunday's race, McLaren could be on the back foot.
Norris thinks the bold setup choice could see them struggle in a straight line and when DRS is active.
“Yeah. I would say the result has been good for Oscar," Norris said to GP Fans Dutch senior editor Jan Bolscher as well as other media. "Overall, we probably struggled a little bit more with pace compared to the leaders, compared to where we were.
"But I think we're just not in the optimal range of downfalls. I think we went for a bit too high and that's costing us, you know, probably close to 6, 7, 8 tens, just on the straights alone.
"And then you're adding clipping and the battery harvest. It can easily be up to almost a second in the straights during the race.
"But obviously again, a decent back in the corner, so there's always this little to and through, but maybe just not in the optimal place, which is, I guess, a penalty of just having everyone qualifying on Friday. We just weren't able to set the car in the row window.”