Rob Smedley has labelled the Japanese Grand Prix "really disappointing" for Williams after it failed to challenge Ferrari for a spot on the podium.
Behind the Mercedes drivers, Williams split the Ferraris with Valtteri Bottas and Felipe Massa qualifying third and fifth at Suzuka. However, Massa finished 17th after sustaining a puncture at the first corner, while Bottas was forced to settle for fifth behind both Ferrari drivers.
"Not our best race, not by a long shot," head of performance engineering Smedley said after the race. "There are things that we need to think about and keep improving on. Without going into a great deal of detail we didn't operate completely well today. The car was a little bit slower than we thought about going into the race - we're talking small margins but it was enough that we weren't actually quicker than Ferrari but a couple of tenths slower. Overall it was a really disappointing day for the team."
Despite dropping behind Sebastian Vettel at the start, Bottas managed to get ahead of Nico Rosberg at Turn 2. Bottas held on to third after the opening stint when Williams successfully completed the undercut on the Mercedes driver. However, Rosberg managed to pass Bottas a lap later at the final chicane.
Bottas then dropped back into a battle with Kimi Raikkonen and the Ferrari driver managed to rise to fourth in the second pit stops. With Bottas unable to match Raikkonen's pace he had to settle for fifth and Smedley admits the team's strategy could have been better.
"I think we made the right decision with the first stop with Vatteri, to retain the position ahead of Rosberg. That was good and made them think a little bit. But the second stop they jumped us - Rosberg actually passed Valtteri on track, even though strategy-wise we'd put him out in front the pace of the car compared to Mercedes allowed Rosberg to get past. Then we had Raikkonen sat behind and we just probably weren't quick enough to react and get that final set of tyres on and keep him behind as well. Very disappointing."
With neither Red Bull scoring a point Williams extended its lead over the Milton Keynes outfit in the battle for third.
Asked if that was a positive, Smedley replied: "It is, in a race like that is the primary thing we need to do so very happy to claw ten points on them. That is a positive but not enough of a positive. They didn't score anything so it was a race where we should have had 18, 20 points on them, not 10."