Nico Rosberg concedes Mercedes are in a battle to finish third in India as the Red Bulls appear unbeatable after Friday's practice.
Sebastian Vettel set the pace in both free practices at the Buddh International Circuit on Friday with Mark Webber making it a Red Bull 1-2.
Rosberg, though, came closest to challenging in FP1 before a scrappy lap on the soft tyres in the afternoon saw him finish the day sixth quickest.
The German's best, a 1:26.582, was 0.860s adrift of Vettel's P1 time.
"That was quite a tough day for us: we learned a lot but still have a lot of work ahead tonight so that I can find the best set-up," he said.
"Generally, it seems that the main question this weekend is who can get third position behind the two Red Bulls, because they look pretty unstoppable at this circuit.
"But I'm confident we will have a role to play in that battle tomorrow and on Sunday."