Lewis Hamilton believes the changes Mercedes and Ferrari make overnight will be “crucial” to who takes pole position at the Abu Dhabi Grand Prix.

Sebastian Vettel set the pace from Hamilton in the first practice session on Friday before the pair swapped positions in FP2. While the second session is more representative because it starts at the same time as qualifying and the race, the top two were separated by less than 0.15s on both occasions, with a Red Bull in third place.

Asked if he felt comfortable with the gap to Ferrari and Red Bull, Hamilton replied: “Definitely not.

“You can see it’s a tenth or something between us. It’s quite close. It’s good that it’s close between us and I think the Red Bull has more to come. It’s closer than you would think. I think it’s going to be crucial for set-up changes you make overnight and also getting some laps together tomorrow.

“It’s been a really good Friday, it’s been really positive, lots of good information today, lots of laps. Really long sessions, they felt like they went on forever and it’s quite hot. It’s more physical here than it’s ever been, because the cars are quicker than they’ve been in the past – hot and your heart rate is higher than usual so it was a good work out today.

“I definitely feel it more after this Friday than last year. And the car’s feeling good – we’ve got some improvements to make on both long and short runs but it’s very close with Ferrari I think it’s like within a tenth.”

And Hamilton admits he will be making a number of changes to his own car overnight despite setting the pace in FP2.

“Yeah we’re changing quite a few things, trying to find the optimum balance aero-wise. Because that’s really just generally for different teams… There are tracks where you’re high downforce, low downforce, medium downforce and having the car work optimally in those different windows.

“[Abu Dhabi is] between high and medium in the corners – this is particularly one of those circuits so we did have some testing to do to find the optimum setup.”