Lewis Hamilton was at a loss to explain why Mercedes is so far off the pace in Singapore after he and Nico Rosberg qualified only fifth and sixth tonight.
Hamilton said he was happy with the feel of the car, but was mystified by the loss of speed relative to rivals.
“The only way I can really explain it is it’s a bit like doing a good lap on the prime tyre, then you go and do exactly the same lap on an option tyre, but it’s a second and a half faster,” he said. “And then I do the lap, and say it’s a really good lap, but it’s a second and a half slower than the guys up ahead. We’ve not lost any performance on our car, the drivers have not lost any performance, so there’s only one way it can come from, and that’s obviously the rubber. But I don’t know why it is the case.
“I’m very interested to find out. I actually challenge all of you guys to go and find what the reasons may be, I’m challenging my team to find out what is, where we lost time, whether it’s in tyre pressures, temperarures blankets, ride heights, I’m challenging everyone to find out, because I want to go and win tomorrow.”
Adam Cooper's F1 Blog 
Mystify him. He should listen to armchair experts in this case, they like to be challenged. Me, I sit on them tyres.
Let’s see what he can do in a sub-par car now that he wants to carry Senna’s baton.
Bernie told them to sandbag, you know, for “the show”.
It’s obviously a tyre issue … and while I don’t see how it could be worth that much time, it is suspicious that suddenly – after getting caught with their hand in the cookie jar, & escaping punishment on a technicality – the Mercedes is only as fast as everyone else when they are now forced to run the tyres within the specified parameters & the eyes of the world and the official are on them.
What I found most interesting when they were caught at the last race, was the pretty big differences in pressures across the 4 tyres on the car.
Was left wondering whether that was a magic bullet they found in all the mountain of data they gathered during their illegal Pirelli test a couple of seasons back …
Your thoughts mirror mine, but we will have to wait until Suzuka to be more certain. Until then, I hope we will enjoy a good race in Singapore…