Shanghai: Red Bull were struggling to replicate the dominance of previous seasons on Saturday after two-time reigning world champion Sebastian Vettel failed to make the third qualifying round for the Chinese Grand Prix and will start 11th.

This time last year the 24-year-old German had won both the opening races -- and he hardly looked back after that as he and his Red Bull car obliterated the opposition.

But after two years of superiority, Vettel finds himself in the unfamiliar position of playing catch-up already, as his patchy season reached a new low in Shanghai.

"I was pretty happy with the car in qualifying," he insisted, despite seeing fellow German Nico Rosberg storm to pole position in his Mercedes for Sunday's race with a time that was almost one second quicker than Vettel's.

"I think we made a step forward compared to the morning (practice). In the morning we had quite a bit of oversteer."

Much has been made of Vettel's new car set-up and in particular his exhaust lay-out, but he refused to use that as an excuse.

"It was just not quick enough at the time. It was a special session if you look at other people: run to run the times were quite different, more than half a second for many people.

"I don't think it's right to blame the package now. In terms of long-run pace I was pretty happy. We should be in good shape.

"Today the pace of the Mercedes was a surprise. Nico made a very strong lap and at the end he out-qualified everyone by half a second. It will be interesting to see how they do in the race, but McLaren is still the favourite."

The affable Vettel denied it was tough adjusting going from the clear champion to what would appear, two races in, to be a season of relative struggle.

Vettel, who came second in the first race in Australia but finished out of the points in Malaysia, said: "It's not a problem, it's not as if we expect to have the best car.

"Even if you have the best car you never really think about that, you try to improve with what you have. For now there's nothing wrong.

"We know we are not where we want to be. Probably we are not there in terms of the competitiveness that we had last year, no doubt, but we need to work and improve the car, that's the only way to come back.

"Being completely honest, we can look at ourselves and our work that we've done (and say) we got everything out of the car that we could today and did a really good job in qualifying, though for sure the result is not good enough."

His Red Bull teammate Mark Webber was seventh-fastest, and admitted it had been a far from ideal qualifying session.

"The Q2 (second qualifying) lap wasn't bad, but I didn't get the Q3 lap together as I would have liked," he said.

"It's a bit all over the place with pulling a lap time together on the soft tyre, but I would have liked to have finished a row further up."

Christian Horner, Red Bull team principal, was more forthright, labelling it "an ultimately disappointing qualifying".