Lewis Hamilton - 4th: "Looking after the tyres here is going to be a real challenge. The track surface is extremely hot, and the amount of energy that goes through the tyres under braking is incredible: the temperatures keep on rising until it feels just like driving on an ice-rink.
"Tyre degradation will be a big issue for everyone around here and the weekend will be all about who can look after the tyres the best.
"Wind direction also played a huge role today. On one lap, there'd be a headwind going into Turn Four, the next lap, it'd be a tailwind, then a crosswind. And that makes a big difference around the circuit. I think my fastest lap was set half an hour after Nico [Rosberg] set the fastest time of the session, and the wind was very different.
"In general, Mercedes looks quick. We're there or thereabouts, but we'll know more tomorrow. Overall, a tough day; a tough challenge, but we're all in the same boat."
Jenson Button, 6th: "I had an interesting day trying to find a balance on both types of tyre compound. The car's been acting very differently from how it's been in the first three races. Perhaps we've gone too far with the balance and need to take a step back - there'll be a bit of work needed tonight to get us into a better position. But I'm hopeful of resolving the issues before tomorrow.
"My times haven't looked great all day - over a single lap, the Mercedes and the Red Bull both look quick. There's a big margin to the front at the moment - but I don't think it will be the same in the race. However, ignoring the times, I just don't feel completely happy with the direction we've chosen. We've started talking about what we can do for tomorrow and there are already some positive comments about which direction to take.
"It's going to be difficult for all of us out there - it will be all about what tyre we can get to work."
Martin Whitmarsh, Team Principal: "A tricky session here in Bahrain today - in this morning's session, neither Jenson nor Lewis felt completely satisfied with the car's balance, and we spent the afternoon pursuing a number of set-up options in order to establish a clearer direction for the remainder of the weekend.
"After P2, it's clear that we're still following that path, but, as always, we have plenty of data to sift through overnight. Jenson and Lewis have also provided the team with some excellent feedback, which dovetails nicely: it's now the role of the engineers to assimilate that into a useful set-up direction for tomorrow.
"While the laptimes don't reflect it, our long-run pace looks reasonably promising, and I'm confident that we'll establish a good baseline for tomorrow's running."