Jenson Button was disappointed and confused after a lack of pace saw him miss out on a position in the final qualifying segment in Spain.
Quickest on the soft tyres in Friday's practice, Button failed to repeat his efforts on Saturday as he just lacked the pace needed to fight at the front.
The Brit was heard telling his McLaren team that the car had "massive understeer, the rear end still is not stable."
His complaints translated into results as he dropped out in Q2, sitting in 11th place.
"I don't know where it went wrong. All day I've struggled with balance," the 32-year-old said.
"We were quickest on the soft tyre yesterday. I thought we would be reasonably competitive and at least get into Q3 but that's not the case.
"I haven't changed that much but struggled with the balance. I don't know why.
"That final run, I had a lot understeer. We're out in Q2 and it doesn't help because we don't have any option tyres left for tomorrow.
"I think Lewis Hamilton should easily get pole position as he's the only person left with fresh soft tyres."
Button, though, was not the only big-name driver to falter as Mark Webber also dropped out in Q2, down in 12th place.
However, Webber at least understood where it all went wrong as he decided to stay in the pits believing his time was good enough to see him through. It wasn't.
"The first lap in Q2 was very competitive but it lulled us into a false sense of security so we parked up the car," he told the BBC.
"The times kept coming and I realised that it was going to be tight with about 50 seconds to go but it was too late by then, you are committed to a strategy."
They were joined in their woes by Ferrari's Felipe Massa as, for the fifth time this season, the Brazilian failed to shine in qualifying.
"I took a lot of traffic on my timed lap," he said. "I had to change completely the direction on track and I lost three of four tenths."