Although he was able to get the maximum out of his car in Singapore, Nico Rosberg admits Mercedes "don't really understand why Red Bull and Ferrari were so much quicker".
For the first time this season there was no Mercedes car on the front row of the grid as Lewis Hamilton was 1.4s off the pole position time of Sebastian Vettel in fifth place while Rosberg started sixth.
Hamilton managed to move up one place as he got ahead of Daniil Kvyat on the undercut on race day, but he was forced to retire due to a software glitch while Rosberg ended fourth after he also managed to get ahead of the Russian after the second round of pit stops.
It was a solid display from Rosberg, but he admits everyone at Mercedes is scratching their heads of their slow pace at the Marina Bay Street Circuit.
"Singapore was a disappointing weekend for my team. We were far off the pace the whole weekend and Lewis' car had to retire," he said. "So I really hope that these were unique circumstances and our car didn't suit the track and conditions.
"The problem is that we don't really understand why Red Bull and Ferrari were so much quicker here."
Rosberg also had some problems before the start of the race as his car switched off a couple of times while he was making his way to the grid. However, he got going and finished fourth in the end.
"The start of the race was a bit chaotic. In the installation laps my engine went off a few times, so I couldn't do the same start procedure, which I practised 100 times," he said.
"I had to adapt but it worked out okay, so I was able to keep the positions. P4 was the maximum today, so we have a lot of work to do for Suzuka to understand what went wrong."