'Small things' cost Williams F1 team a podium in US Grand Prix

Valtteri Bottas and Felipe Massa started on row two of the grid for Sunday's Austin F1 race, but the Red Bull of Daniel Ricciardo defeated both drivers.

Massa fell behind Ricciardo after a delay at his final pitstop, and Smedley told reporters after the race that several small factors around that stop conspired against his driver.

"It would be naive of me to say we're not disappointed starting third and fourth and finishing fourth and fifth - we dropped five points as a team so it didn't go exactly according to plan," Smedley said.

"In the second stop we thought we had a reasonable margin on Daniel, which was about 2.5 seconds when he pitted.

"But a lot of small things that went against us: the third sector of the in-lap wasn't perfect, the pitstop itself we lost a second, and we had a lot of wheelspin getting away from the pitstop.

"All of that culminates in a 2.5 seconds margin gone all of a sudden."

Smedley praised Ricciardo's efforts and said Williams had also been caught out by how long the medium-compound tyre lasted in race conditions.

"Daniel probably had a bit of pace on us today and he made it count when he needed to," Smedley added. "He did a really good job today.

"I don't think we expected it [the medium tyre] to be such low deg.

"We need to go away and have a look and see why we effectively went into the race with the wrong assumptions on tyres.

"It won't do and I hope we do better next time."

Massa said his worsening tyre life in the closing stages compared to Ricciardo made it impossible to use his superior straightline speed to attack.

"Being behind we were using a little bit more the tyres - that was the problem, but the pace was good," Massa said.

"When I was in front everything was much easier - I was even opening the gap - but being behind it was a little bit more difficult."

BOTTAS STRUGGLES