Dr Helmut Marko is not sounding confident about a Max Verstappen victory this Sunday at Spa-Francorchamps.
The triple world champion bounced back from Hungary with strong pace in opening practice at his favourite track on Friday, but was then outpaced by both McLarens in FP2.
"We’re in the running," team boss Christian Horner insisted. "According to our measurements, (Lando) Norris was using the engine more than us.
"We’re comparing ourselves more with (Oscar) Piastri," who was a mere 2 thousandths faster than Verstappen.
After the debut of the vastly-different engine cover without the familiar lumps in Hungary, the old version was back on Verstappen’s car on Friday. But Horner says that was always the plan.
"We are only using the different engine cover," he said. "The rest of the car is the same. This has always been the plan for the fast tracks - here and Monza.
"We change depending on the circuit."
And while Sergio Perez is still using the pre-Hungary specification, Verstappen did try a new wave-shaped rear wing in Belgian GP practice.
Verstappen also has a new power unit fitted - which will cost him ten places on the grid. "It will be very difficult on Sunday," team consultant Marko admits.
"At the moment it does not look like it will be a victory. We will see if we can make any setup changes, but we are not so worried about McLaren’s pace. It’s about finding the right balance in the car."
Also on Friday, the FIA ordered all teams to attach prescribed reference stickers and cameras on the front wings, as the governing body tries to understand the cars’ new flexibility tricks.
"The intention is to measure all front wings over several race weekends," an FIA source said. "The data we collect will lead to a better general understanding of flexibility in order to define future regulations."