Williams' head of performance engineering Rob Smedley says that a lack of understanding of the Pirelli hard compound tyres held them back last week in Suzuka.
Smedley had already admitted that he was deeply disappointed with how last week's Japanese Grand Prix turned out for the team.
A slower-than-expected car in comparison with the Ferraris and a sluggish second pit stop were among the reasons Smedley gave for Valtteri Bottas dropping from third place on the grid to fifth position at the finish, while his team mate Felipe Massa's day was effectively ruined by contact with Daniel Ricciardo in turn one.
But for Smedley, perhaps the more worrying longer-term problem was the team's miscue when it came to tyre strategy at Suzuka.
"I think that the tyres probably were a bit more durable than what we expected, especially the prime. The prime turned out to be a lot more durable and have a lot longer life than we were predicting.
"When we stopped, apart from Hamilton who was kind of running his own race, all the teams around us who we were fighting - two Ferraris and Mercedes with Rosberg - they stopped to fit a prime and we stopped to fit an option.
"That's something that we need to understand as a group," he admitted. "Something else we need to take a look at that didn't go swimmingly."
Smedley added that despite pre-race worries among all the teams on the grid, concerns about tyres overheating and 'ballooning' hadn't proved to be a factor in the race itself.
"No, it was about as much as we were expecting," he said, adding that there had never been much doubt at Williams about the proper race strategy at Suzuka this year. "Quite an easy two-stop."
Many fans were surprised that Williams opted to keep Massa out on the track for the entire race and not retire him early after his first lap clash in order to save wear and tear on the car and power unit. The Brazilian had to pit for repairs and ended up running two laps off the leaders and finished in 17th place.
"Was it ever the right time to retire him? I guess we were waiting for a safety car in that [first] pit stop that never came about. We're here to race, and that's the instruction that we're here to race so we complied with that."
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