Silver Arrows team boss Toto Wolff praised Lewis' pole effort, especially after a tough Friday, but warned that the Ferraris are still to be feared, even if Sebastian Vettel will start Sunday's race from the back of the grid, due to an engine problem.
"So far this weekend we have seen a pretty confusing picture of performance, with different cars quick at different times and even big gaps between team-mates," said Toto.
"Our struggle has been to get the tyres into the right working window, then things came together this afternoon as the track temperatures cooled.
"After a tough Friday, the team here at the track and back at base did a good, calm job to analyse the situation and come up with some improvements. And then, when it really counted, Lewis was able to put together a blistering lap to take pole - something we didn't expect at all going into qualifying. It was really a great job from him.
"Valtteri found it harder today but it's clear that tiny differences in set-up or tyre temperatures are making a big difference in lap time, and it didn't quite come together in Q3.
"There's no doubt this session was also a tough moment for Ferrari, with Sebastian unable to take part, but there are no points scored on Saturday. They have had the strongest race pace this weekend and will be a serious threat in the race.
"We can't pretend that we have all the answers right now, but we can be pleased with the outcome today and are ready to fight hard in the race."