The Silver Arrows were narrowly edged out by the Ferraris in an intense Qualifying Shootout around the Sochi Autodrom.
Scuderia Ferrari edge the Silver Arrows
Valtteri claimed P3 on the grid in an ultra-tight session, where the top three were covered by just 0.095s. Kimi Raikkonen had looked set for his first pole since 2008, until Sebastian Vettel shunted his team-mate down to P2 in the dying seconds of the session.
He pushed them all the way, but Valtteri conceded that the Ferraris were simply just too quick on the day.
"I think we can see Ferrari were quicker today," he said. "We were close in the end, but not close enough.
Valtteri: We were close in the end, but not close enough
"All weekend they've had the upper hand and they've managed to extract more out of the tyres. They are looking very strong here and, as we've seen so far this year, Ferrari have a good race pace and we expect it to be the same tomorrow.
"We made an improvement from yesterday: it wasn't quite enough but I think the changes we made overnight should help us in the race.
"Tomorrow is where it counts and starting on the second row is still not a bad place to begin the race. There's a very long run down into Turn 2 and a lot of slipstreaming. Ferrari is ahead today, but hopefully not tomorrow."
Lewis: I just wasn't quick enough today
Lewis had to settle for P4 on the grid, on what was a trying day for the triple World Champion. A messy final sector left him half a second adrift of Valtteri. Not one to let his head drop, Lewis is looking ahead to Sunday.
"I just wasn't quick enough today," said Lewis. "It was all in the last sector, I was losing half a second there. I've been struggling there all weekend with the balance and it's been tough to utilise the tyres. We'll go back to the drawing board tonight and try and improve.
"Ferrari did a great job. They look quick on race pace and my race runs weren't great yesterday, so it's going to be tough. But we'll give everything we've got.
"Sochi isn't the easiest track to follow on, but there are long straights which should offer the opportunity to move forward. That's our goal.
"I'm on the dirty side of the grid so I haven't done myself any favours off the start. But that was the best job I could do today. We've got a real race to look forward to. There's no point being upset; we'll channel our positive energy and hopefully Sunday will be better."
Toto: We're the hunters and not the hunted
Head of Mercedes-Benz Motorsport, Toto Wolff admitted that the day had been tricky, but still reckoned that Valtteri was unlucky not to walk away with pole.
"Today's result showed that, while Ferrari and ourselves are a long way ahead of the other teams, it's still a work in progress for us to get the car into the right window and performing consistently," said Toto.
"We made a good step compared to yesterday but this afternoon, the top three were covered by less than a tenth of a second and Valtteri could even have been on pole with his final lap until a small mistake in the last sector.
"As for Lewis, he hasn't been happy with the car, finding it tricky to drive, and this is a place where you need to feel good with the car to hook it all up. So we start from the second row tomorrow and now it's our job to look forward and see what the race can bring.
"As the hunters and not the hunted, maybe we have some different cards we can play to chase the race victory."
James: It always hurts when you're not at the front
Technical Director James Allison was pleased with the progress overnight, after a tough Friday. But feels there is more to come, predicting a strong race on Sunday.
"It always hurts when you're not at the front and even more so when the gaps are so small," said James.
"After struggling yesterday in practice, we did a good job to unlock the performance of the car overnight and made a good step forward relative to our competitors and Ferrari in particular.
"However, it wasn't quite enough to get either car on the front row. We will knuckle down this evening, prepare thoroughly and look forward to a strong race tomorrow in what are expected to be broadly similar conditions."