Nico Rosberg was happy with the way that his Friday practice had gone, but said that he was also well aware that the real work in Austin still lay ahead of him if he wants to consolidate his lead over Mercedes team mate Lewis Hamilton in the world championship battle.
"It's been an okay day for me," he said after topping FP2 by almost two tenths of a second ahead of Red Bull's Daniel Ricciardo, with Hamilton a further tenth back in third.
"Today doesn't count for anything, it's just getting to grips with the track.," he cautioned. "That doesn't count for much on the Friday. But in general it's a decent start.
"It's been a decent start to the weekend. It's been good to drive out there, it's a great track. We found a good balance in the end, on one lap and also on the race run it was okay.
"It seems Red Bull is our closest competitor again," he added. "Just as they have been in the last couple of races. They've been pretty close and I think it's no different here.
"Apart from that it's going to be interesting tomorrow because the wind is going to change 180 degrees so completely different.
"Difficult to imagine but it transforms the car totally out there, so maybe whatever we learned today won't really apply tomorrow and we'll start from scratch so that will be a challenge."
The big question for everyone will undoubtedly be tyre strategy, with all the teams apparently struggling to realise the potential in the supersoft tyres on Friday.
"For the race it's not clear cut yet because the supersort is really struggling on race pace so maybe there will be some people doing soft, some doing supersoft to start the race.
"I'm sure we can get through to Q3 with soft tyres - no, not sure, but I think so - but is it the right thing and start with that tyre in the race? I'm not sure yet. We have to wait and see. But there may be some people trying tha."
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