Jenson Button is unsure where the speed he showed in Friday practice has gone after failing to reach the last segment of qualifying at Barcelona.
The Englishman had complained about a lack of balance on the faster soft tyre through qualifying and this morning's practice session, but the team was unable to make the changes needed to solve the issue despite adding more front wing during Q2.
"To be out in Q2, not by a mistake but by not being quick enough is really surprising. It is going to be a tough afternoon tomorrow," said Button, who had been quickest on Friday.
"I didn't get anywhere near the balance I had yesterday in practice. I had a very loose rear end for most of qualifying and then we added more front wing at the end because we had some understeer in the high speed, we did that and that added to my problems."
It is the first time since Spa 2011 that Button has failed to get into Q3. He will line up next to Mark Webber, who qualified in 12th position, but has saved four sets of new tyres, which Button thinks could be decisive in tomorrow's race.
"I'm out in Q2, and it doesn't really help because we don't have any new tyres left. It is very close around me, not many people have new tyres, but Webber does," he said.
"If the balance is like this I am going to struggle [in the race], but hopefully we can work out why that is."