The team recognised that the issue was that Russell was less comfortable with the car in the medium and high-speed corners of the middle sector. That meant he was making corrections to the steering that Antonelli did not have to do. These cost speed, which needed to be filled in with battery power. As electrical energy is limited, that left Russell down on deployment in the final third of the lap.
But after hard work over the weekend Russell made significant inroads into that issue, and Mercedes admitted they were still seeing a straight-line discrepancy that they could not yet explain.
Russell, who heads into the race 25 points behind Antonelli, said: “There’s a serious issue at play here and the team are working so hard to resolve it.
“But every lap I do, when I see I’m down anywhere from 0.2-0.6secs in the straights, it’s pretty infuriating.
“My whole focus for the last 36 hours has been on straight-line speed. It hasn’t been focused on the set-up, the tyres or anything, because we’re all trying to solve what is going on. And even my last lap, for some reason, I lost another 0.15secs to myself, just on the straight.
“You’re watching (the display) on your steering wheel, just losing speed when you’re full gas in the straight. You feel powerless. So, we don’t know what’s going on.
“I don’t think it’s the power unit, to be honest. But there’s something slowing us down in the straights. And the team are really, really on it now to try and solve it.
“Battling against Kimi is very tough in a fair fight. When we are in this situation, it’s impossible.”
Mercedes trackside engineering director Andrew Shovlin said: “George continued to suffer from poor deployment into the final chicane, which cost him a grid position.
“We’re investigating what’s causing this as a priority as there is a clear loss that we cannot explain by driving style.”
McLaren, whose use Mercedes customer engines, were seeing an almost identical split in deployment across the cars of Lando Norris and Oscar Piastri.
Team principal Andrea Stella said: “If I compare Lando and Oscar in their best lap in Q3, Oscar is losing time in the final straight and Blanchimont for reasons that have nothing to do with Oscar’s driving.
“They are just a minor deviation in how the power unit was operated. And I think this seems to be pretty much the same across the two Mercedes cars. When you overlay Antonelli and Russell, it looks like Lando and Oscar.”
Piastri and Russell were both seeing their straight-line speed cut earlier into the first corner, La Source, than Norris and Antonelli, before both had similar losses in the final sector.
