Ferrari shot itself in the foot with its tyre choice when the Formula 1 Australian Grand Prix was red-flagged to clear wreckage from Fernando Alonso's huge crash, says Pat Symonds.
When the race was stopped after Alonso collided with Esteban Gutierrez, Mercedes chose to switch Nico Rosberg from super-softs to mediums, while Ferrari kept race leader Sebastian Vettel on super-softs, meaning he would have to make another stop before the end of the race.
Vettel was unable to build a gap to Rosberg before his stop, emerging behind the eventual race winner and one-stopping Lewis Hamilton to drop to third.
"Ferrari shot themselves in the foot," said Williams technical director Symonds.
"I don't really understand what their thinking was.
"It was contrary to the way we were planning.
"Before the race we said we would try and get in a position to do a one-stop race.
"Our thinking had been that way, so we were a bit more biased to the harder tyres."
While Symonds was surprised by Ferrari's decision, he did accept the team had to mix-up its strategy to give it a chance of beating Mercedes.
"I said in my strategy briefing to the team that Ferrari had to do something different," he added.
"They weren't going to beat Mercedes doing the same thing so maybe that was their thinking.
"They just needed to do the opposite of whatever Mercedes were going to do.
"I don't know if they had a chance of winning as Mercedes may have had something in hand.
"The fact Mercedes did get through after [dropping back at] the start shows they have got a lot of pace."