BARCELONA (AFP) - Sebastian Vettel was left perplexed by Ferrari's loss of performance on Saturday when they slipped back to the third row of the grid for Sunday's Spanish Grand Prix.

Ferrari had looked likely to mount a bid for the front row after strong showings in free practice, but that pace appeared to evaporate in qualifying.

German Vettel, who was quickest in first free practice on Friday, wound up sixth behind his Ferrari team-mate Kimi Raikkonen of Finland.

Defending champion Lewis Hamilton grabbed his first pole position in three races ahead of his Mercedes team-mate Nico Rosberg.

"We're disappointed as a team today because we didn't deliver what we can," said four-time world champion Vettel.

"We need to have a look and understand. We can't change it now.

"I think the car should be a lot quicker tomorrow (Sunday). I don't know what happened this afternoon, but tomorrow is another day.

"We know that the car is strong. We know that the car can be very strong and we just need to make sure that we get it in the right groove."

Rosberg said he was surprised at Ferrari's form.

He explained: "We are not supposed to be so far ahead, but we are surprised at how quick Red Bull are... It is all changing quite a bit, but the only constant is us...

"That is impressive to see. It's a great job from the team. On every track, we keep the car working perfectly and that is fantastic."