The team admitted that the problem was that Russell was less comfortable with the car in mid- and high-speed mid-sector corners. This meant that he made adjustments to the steering, which Antonelli did not have to do. This is the cost of speed that had to be made up by charging the battery. With limited power, Russell was unable to turn in the final third of the lap.
But after hard work over the weekend, Russell has made significant progress on the issue and Mercedes admitted they still see a straightforward discrepancy that they cannot yet explain.
Russell, who goes into the race 25 points behind Antonelli, said: “There is a serious problem here and the team is working so hard to solve it.
“But every lap, when I see that on the straights I’m 0.2 to 0.6 seconds behind, it really pisses me off.
“For the last 36 hours my entire focus has been on straight line speed. I wasn’t focused on the settings or the tires or anything else because we’re all trying to figure out what’s going on. And even on the last lap, for some reason, I lost another 0.15 seconds, only on the straight line.
“You watch the (display) on the steering wheel, you just lose speed when you get full throttle down the straight. You feel powerless. So we don’t know what’s going on.
“To be honest, I don’t think it’s the power unit. But on the straights something slows us down. And the team is now trying very, very hard to solve this problem.”
“Fighting Kimi in a fair fight is very difficult. When we are in this situation, it is impossible.”
Mercedes track technical director Andrew Shovlin said: “George continued to suffer from a poor spin at the final chicane which cost him his grid position.
“We are investigating the cause of this as a priority as there is a clear loss that we cannot attribute to driving style.”
McLaren, whose company uses Mercedes engines, used almost equal numbers of Lando Norris and Oscar Piastri cars.
Team principal Andrea Stella said: “If I compare Lando and Oscar on their best lap in Q3, Oscar is losing time on the final straight and Blanchimon for reasons that have nothing to do with Oscar’s driving.
“This is just a minor deviation in the operation of the power unit. And I think it’s about the same for the two Mercedes cars. When you put Antonelli and Russell on top of each other, it’s like Lando and Oscar.”
Piastri and Russell saw their straight line speed drop earlier into La Source’s first corner than Norris and Antonelli, before both suffered similar losses in the final sector.