Formula One: Vettel satisfied with third on Spanish GP grid

Defending world champion and championship leader Sebastian Vettel said he was satisfied with qualifying third on Saturday for Sunday's Spanish Grand Prix.

The world championship leading German, in his Red Bull, was unable to keep pace with the two Mercedes driven by pole sitter Nico Rosberg and Lewis Hamilton.

He said: "I am quite happy to be honest. Yesterday and this morning I was really happy, and I think we improved the car so I think we are in good shape."

Only once has a driver who failed to qualifying on the front row won the race.

Vettel added: "We took a different approach to the majority of people, using option tyres only. Whether that helps us tomorrow we have to wait and see.

"It will be a long race, it will be about tyre degradation. Now, with the conditions helping a little, it is a tough challenge, the tyres don't last as long as we would like."

Although Mercedes drivers Rosberg and Hamilton voiced pessimism about their race chances, Vettel said he did not believe the 'silver arrows' will be easy to beat or that Lotus and Ferrari are out of contention.

"Mercedes are in front of us right now, and to be honest they had some long runs and didn't look too bad," said Vettel.

"On the long runs yesterday both Ferrari and Lotus were pretty competitive, so we can expect them to be very strong in the race as well. It is going to be tough."

Rosberg says he is concerned about tyre degradation after falling from pole to ninth place in Bahrain last time out.

"It has just been working really well all weekend, we've optimised everything," he said.

"But after what we saw in Bahrain it is nice, but we cannot be over confident when we're thinking about the race result. We're surprised to be that quick, but it was a good qualifying and a good lap in the end, so I'm really, really happy with that.

"It's a good boost for the team, the front row is fantastic but of course we have to be a bit cautious after Bahrain."

Rosberg is confident that his team has made progress in terms of its tyre management, but is unsure if it will be enough to challenge for victory.

"The team has been working really hard to be even better, understanding how to get the most out of these tyres," he said. "We were a bit behind in Bahrain, and we come here and there are issues again.

Hamilton seemed surprised to be on the front row after losing his way on car set-up for the race.

"I haven't had the best of weekends up until now," said Hamilton. "This is still great for us today to be one-two on the grid, but I have been struggling all weekend. The long runs were pretty poor, but on one-lap pace the car doesn't seem to be too bad.

Rosberg warned that maintaining Mercedes' pace over a race distance would be tough, and Hamilton agreed that victory did not seem realistic. "We will do the best job we can from the start, but more of a concern is looking after the tyres," he said.

"I love that we are going to try and get into Turn 1 first, that will be really good for the team. We have to improve our race pace. We have very good qualifying pace. I hope in the future we will get that win."

He also denied being disappointed at being overshadowed by his team-mate for the second qualifying session in a row.

"Sometimes you get beaten, sometimes you go ahead - that is the name of the game," Hamilton said. "At the end of the day he is quicker today and I just have to work harder - simple."