Lewis Hamilton admitted he was struggling with the rear of his Mercedes W15 after Thursday’s practice sessions at the Saudi Arabian Grand Prix, with the seven-time world champion suffering some “really big moments” out on track.

While team mate George Russell found himself near the top of the timesheets in both practice hours, Hamilton did not appear as comfortable with the car throughout the running at the Jeddah Corniche Circuit.

The second session proved particularly challenging for the 39-year-old. As well as reporting a loss of power in the final moments of the hour, Hamilton was also investigated afterwards over an impeding incident with Logan Sargeant, with the Williams driver having to take avoiding action after approaching the slow-moving Mercedes.

A warning was issued to Hamilton and Mercedes over the matter, and the team were fined €15,000 for failing to tell Hamilton that Sargeant was arriving on a fast lap.

Speaking after FP2, Hamilton reflected on his tricky session, explaining: “Yeah, a typical day, just lacking the confidence in the rear of the car. [With] the set-up we did some work session to session, changed quite a bit, but [there was still the] underlying issue with the rear end that I was struggling with, so I had a couple of really big moments out there.

"In these high-speed areas you need to have full faith in the rear of the car and I don’t have that yet.”

On his expectations for qualifying, Hamilton said: “I don’t know, we need to go through the data but George is obviously a lot happier with his car. We went in different directions today, trying different things to find the right solution for the car, but yeah, all I want is a stable rear and then I’ll be happy, so that’s what we are working on.”

It certainly looked to be a more positive day for Russell, who ended FP1 in fourth place before putting himself into P2 on the timesheets in the second practice session. Despite this, the Briton suggested that it had been a “scrappy” FP2 hour at times.

“It was fun to be back in Jeddah, such a high-speed circuit, that’s enjoyable,” he commented. “Little bit of a scrappy session, I don’t think we had the car in the perfect window, I think the lap times looked good and in the low-fuel high-fuel pace.

“I don’t know where we are at really but it’s so close again. The Aston [Martins] have been a bit of a surprise, great to see them up there and we have work to do overnight to see what we can achieve tomorrow.”

Asked about how important qualifying is with the track being a street circuit, Russell responded: “Yeah absolutely, but we did a lot of testing today. In FP1 Lewis started with one set-up, I started with one drastically different. Then in FP2 we did the complete opposite, we swapped set-ups to see what worked, to try and learn more about the car, trying to get feedback from us both.

“And it is still early days. We’ve only been at one circuit, it’s a new car, so we need to keep on learning. So as I said, let’s see what we can do tonight. Everybody back at home will be working hard on the simulator and try and eke out a bit more performance.”

Russell feels that it is still “too early to say” how Mercedes’ long run pace looks, though suggested that Red Bull hold the edge in this area.

“For sure Max [Verstappen] is the quickest, Checo [Sergio Perez] is not too far behind,” said the 26-year-old. “But it’s difficult to follow at the moment. The cars are becoming increasingly harder to follow as the years progress and I think it will be tight, as we saw in Bahrain. Ferrari and Aston probably look like our biggest threats and rivals at the moment, but it looks like it’s going to go down to qualifying again.”

As well as the incident between Hamilton and Sargeant, there were other occasions where traffic proved to be an issue during Thursday’s practice sessions, something that Russell also gave his take on.

“It’s always difficult in Jeddah. You can’t have it all,” he conceded. “It’s one of the best circuits to drive, so exhilarating but you can’t see. So it’s definitely challenging.

“The FIA at the start of the year introduced something on our steering wheel to show us the car in front and the car behind and the gaps, which has been a real improvement.

"But the thing is, if you have two cars behind on a slow lap, and a car travelling at 200mph ten seconds behind and he passes through, I think that’s kind of what happened with Lewis and Sargeant, you’ll have one car behind and it will say that direct driver who is behind but you don’t know who is three or four cars behind that on a push lap.