Lewis Hamilton said he felt a “lack of confidence” in the W14 after finishing 14th in the second practice session.
The seven-time World Champion has looked at odds with the Mercedes car of late with the two parties seemingly going back and forth on what they want from the W15.
But there are still seven races left to go this season and judging from the running of Friday, Hamilton could be in for a tough time this weekend.
Lewis Hamilton urges team to rectify Friday errors
The Brit finished P16 in the first session of the day before improving to 14th for FP2 but that will still be far away from what he would expect.
Speaking after the second session, Hamilton said he felt “a lack of confidence” which contributed to his struggles.
“It was a very challenging day for us out there,” Hamilton said. “I had a lack of confidence in the car and that contributed to our struggles.
“It was difficult to find the right balance and we didn’t manage to get on top of it by the end of FP2. The tyres were overheating and that left us quite far off the top of the timing sheets.
“We know we’ve got a lot of work to do tonight to pick up the performance. I do believe we can make improvements though. We have had similar Friday’s this season and come back stronger on Saturday. We will see tomorrow if we have done so again.”
As for his team-mate George Russell, he was up in P5 for FP2 after returning to the track following his dramatic last-lap crash in Singapore.
“It feels great to be back driving around Suzuka,” Russell said. “It’s such an incredible circuit.
“It’s been a slightly strange Friday for us. The track seemed to have very low grip, particularly in FP1, so the car is sliding around quite a lot. That doesn’t give you the best feeling in the world as a driver. Particularly when you’ve got plenty of high-speed corners to tackle. The race on Sunday will also be interesting as tyre degradation looks very high.
“In terms of the relative order, the Red Bull looks to have returned to its normal pace at the front. They have been exceptionally quick today. I think we are likely half-a-step behind the Ferraris and the McLaren of Lando Norris at present.
“We’ve got a bit of work to do tonight to close that gap. We are typically strong at finding those performance gains so we can be optimistic of improving for tomorrow.”