Valtteri qualified seventh and Felipe ninth for the Singapore Grand Prix.
Valtteri set his quickest time on his final run but was pushed down from P5 to P7.
Felipe made a small mistake on his last lap, so was unable to match his best Q2 time.
Williams was closer than usual to both Mercedes, with Valtteri just two tenths behind Hamilton in P5, while Ferrari and Red Bull make up the first two rows.
Rob Smedley, Head of Performance Engineering: We worked on the car last night to ensure we were in Q3 and in front of the midfield, but it's not where we need to be. As a company, everyone at Williams needs to work hard to ensure that we improve in situations like this. There are some fairly anomalous laptimes in qualifying today, so we can see that tyre management played a major part. The positive is that it's going to be a long race with lots of points to pick up, so we'll get as many as we can.
Valtteri Bottas: Given Friday, it's a good starting position for tomorrow. We always knew it was going to be challenging for us here and we improved from practice to get both cars inside the top 10. I'm pleased with my lap, I think I got everything I could from the car so it's a good result. This is a race where anything can happen and we are going to be there so everything is still open.
Felipe Massa: It wasn't an easy qualifying session. I made a mistake in Q3 and lost time that would have put me a few positions further up. We only had one set of new tyres for Q3 so I tried everything I could, maybe too much. The position at the end could have been much better, but this is not a fantastic track for us so we'll concentrate on getting the best we can from the race tomorrow.
Track Marina Bay, Singapore Weather Warm and Dry
Lap Length 5.065kms / 3.147 miles Temperature Air: 28-29°C Track: 33-35°C
Pos Driver Team Q1 Q2 Q3
1. S. Vettel Ferrari 1:46.017 (3rd) 1:44.743 (1st) 1:43.885
2. D. Ricciardo Red Bull 1:46.166 (4th) 1:45.291 (4th) 1:44.428
3. K. Raikkonen Ferrari 1:46.467 (8th) 1:45.140 (3rd) 1:44.667
7. V. Bottas WILLIAMS MARTINI RACING 1:46.231 (6th) 1:45.887 (10th) 1:45.676
9. F. Massa WILLIAMS MARTINI RACING 1:46.879 (14th) 1:45.701 (8th) 1:46.077