Ferraris' Sebastian Vettel has said he fears it might be 'tough' for anyone to stop Mercedes romping to victory in Brazil this weekend.
The world championship team came out top in both of Friday's free practice sessions. Lewis Hamilton set a new track record in the morning with his lap of 1:09.202s, just ahead of his team mate Valtteri Bottas.
Vettel's best time of the day was 1:09.875s, set after lunch.
"Mercedes looked very strong," Vettel said at the end of the day. "I think they are a bit ahead, both of them.
"It will be tough to beat Mercedes as they look very, very quick in all conditions, and on all tyres."
Vettel suggested that Ferrari would have to settle for focussing on the battle for 'best of the rest' with Red Bull.
"I think it's very close between us and Red Bull," he said. "I think we can fine tune the balance and that should help us.
He was at least happy to get a lot of track time on Friday. Forecasts has suggested that it would rain in the afternoon, but in the end there was only a brief light shower.
“I think that in the end we ran more than what we expected as it didn’t rain," he said. "It was nice to be able to do a lot of laps today. It's more quiet on track than off-track, so I enjoy that.
"We need to find the right balance and this should help us get the pace for the qualifying session and the race," he continued.
"But I still think it won’t be easy to defeat our main competitors. We’ll see where we get tomorrow.”
Vettel's team mate Kimi Raikkonen was third fastest in the morning. However, he dropped to sixth after lunch. The Finn blamed tyre-related vibrations in FP2 for the drop-off in performance.
"I felt some vibrations at the beginning of my stint, but that’s quite normal to have sometimes in the car," he reported. "Usually it comes from tires and different sets.
"The tyres will play a key role here as usual. The performance will depend on how they work and how long they will last.
"It’s only a Friday,” he added. "As always, we keep trying different things to learn from them.
"We don’t know what the temperatures will be over the rest of the weekend. But we cannot change them anyway and it will be the same for everybody."
Gallery: The beautiful wives and girlfriends of F1 drivers
Keep up to date with all the F1 news via Facebook and Twitter
