Daniil Kvyat: "I think it was a productive FP2. We were able to use plenty of the track time available and started the weekend on the right foot. We didn't have the full day to correct the balance and issues we had, so we will now look at all of that overnight and see where we can make some progress. We're not too far away of the guys ahead and we will aim to make a good improvement in order to be in that mix."

Brendon Hartley: "A steep learning curve today! It all went pretty smoothly and I kept the car on track without making too many mistakes, so I'm quite happy. I didn't really know what to expect from today because I just had so much to learn! I think I made quite a big progression throughout the day. The biggest difference from what I'm used to is the high-speed grip, it's incredible here in Formula 1... it was quite an eye-opener! Another challenge are the tyres, which are also quite different to what I'm used to. On the other hand, the long-run looks quite positive and I did a good job managing the tyres there - the biggest thing I need to work on now is the new tyre pace, and I'll get another crack at it tomorrow morning before qualifying. All in all, I'd say it's all coming together. We'll now work hard and go through plenty of data tonight and hopefully I'll make another step forward tomorrow."

Sean Gelael: "Another FP1 in tricky conditions... It seems like I'm bringing the rain to each track I'm driving at: it's rained at every single Free Practice session I've had up until now! It's a bit of a shame, but looking at the positive side, I'm well prepared in the wet! We were quite competitive at the start of the session. Then, when the track got quicker, my intermediate tyres were a bit warn out... After that, on the slicks, I got caught in a bit of traffic during my fast lap, so I lost a bit of time there, but overall it's been okay and we were able to do many laps, which is always good. Hopefully next week in Mexico it stays dry!"

Jonathan Eddolls (Chief Race Engineer): "A very busy day. We started off with three completely different drivers to the ones we had at the last race, which was interesting and exciting. Sean was in for this morning's FP1 and he did some really good aero testing for us. This was important to validate some aero components. It was great to have Daniil back in the car - he was in for FP2. It's also been fantastic to welcome Brendon to the team - he's settled in straight away. The target was to give all of the drivers lots of laps. FP1 started off damp, which gave us the opportunity to test a new prototype inter tyre here, so we gave them that to learn and gather some data - it's the same construction but a different compound. From the first run Brendon suffered from significant helmet lift, so we had to make quite a few changes throughout the day to the helmet, as well as adding a windscreen to improve that.

"At the start of FP2 we reached the point where he was comfortable in the car but we'll do some small modifications again for tomorrow, but all in all he's happy and performed very well. Daniil did a great job, getting straight back into it like he hadn't been away. He's really happy with the car and showed good low-fuel pace. We need to look at the high-fuel pace and degradation to see what we can do to learn for Sunday - ours was a little bit higher than expected, so we will look into that. We also had some new mechanical components to test across the cars, so we were also evaluating those today.

"Regarding the fact that Brendon will have a 25 grid position penalty, this is something that affects our decisions for tomorrow; especially in terms of tyre selection. Because we had to choose the tyres for this event several months ago, prior to knowing about the engine penalty, it even affected our choice for today. For Sunday, we're saving more tyres of the harder type for Brendon, to give him maximum flexibility in the race. The focus for him is on long-run performance and giving him a car that he can overtake with in the race, whereas for Daniil, it's a more conventional weekend, so the focus is on pure qualifying performance and not forgetting that he needs good long-run pace as well... The philosophy and set-up across the cars might be different to reflect that."

Check out our Friday gallery from Austin, here.