Red Bull F1 team warns Vettel set for 'big step' in performance

Vettel has struggled to get comfortable with his car under braking and corner entry this year, which means he has not been able to deliver his full potential.

But in the wake of a huge effort from his team to solve his problems, allied to the use of a different chassis from this weekend, the team has faith that Vettel will be back to his best soon.

And having gone through a similar experience with Vettel in 2012, when he struggled at the start of that campaign before turning things around to win the title, Red Bull boss Christian Horner sees potential for a large jump.

"He hasn't found his set-up that he wants yet, because we had such limited time pre-season," Horner told AUTOSPORT ahead of the Spanish Grand Prix.

"He is not getting the feel from the car that he is looking at. But hopefully we are close to unlocking that and as soon as we do, like in 2012, we will see him make a big step.

"Seb is just very sensitive to the car on corner entry, and he just hasn't had the feel from the car mainly due to improvements of engine controls at the moment.

"But as that is getting smoothed out as Renault gets experience, that is only improving."

SPANISH GP A LITMUS TEST

Although Mercedes has been dominant so far this season, Horner still believes there is opportunity for Red Bull to get back to the front despite its difficult start to 2014.

But he thinks this weekend's Spanish GP will deliver the answer as to the real chance his team has - because it is a venue that should play more to Red Bull's strengths.

"Such was the margin that Mercedes has enjoyed since the beginning of the year that all things being equal, one would expect them to be right there and the team to beat again," he said.

"But the nature of this circuit, together with improvements that we are chipping away at, means we can get close to them.

"It tends to be if you have a car that works here it tends to work anywhere - so it is a very good test of form ahead of the European season."

Red Bull's engine partner Renault has expressed some confidence about the steps it has made in recent weeks - and Horner says his outfit has never been more focused on making improvements.

"Mercedes have got themselves into a very strong position but nobody is unbeatable," he said. "We have great team, a great team in strength and depth, and everybody is up for the challenge.

"It has really motivated the team and galvanised the team, who have said, 'okay we have something to chase'.

"It is the difference from being the hunted to being the hunter. There is a real sense of determination in the team to close this gap down."