China - McLaren has admitted it may have missed the mark as it set goals for 2018.
After three abysmal years with Honda, hopes were high as the once-great British team switched to Renault power.
But the 2018 car is also not fully up to speed - notably on the straights.
Not fully up to speed
Team boss Eric Boullier is quoted by Marca: "There is nothing serious or horrible in terms of the design."
READ: McLaren 'almost factory team' by 2019 - Boullier
"But we have to be faster in the corners and on the straights."
The Spanish newspaper said McLaren may therefore be considering a 'plan B' - like a new chassis for next month's Spanish grand prix.
Boullier added: "The two drivers think the same about the good balance of the car, and when we make a setting change, it reacts properly. The car is matching the objectives we set, so it's possible that the objectives were not right."