Adrian Newey admits that Sebastian Vettel has struggled to adapt to the loss of the blown diffuser in 2014, and says that RBR is trying to adjust the car to suit his style.
Vettel was the master of the art of driving with the extra rear downforce that was generated until the use of exhaust gases was completely outlawed for this year.
“There’s a fair bit of that,” Newey told this writer. “Seb has a very particular way of driving, and if we can get the car to suit that driving style, then he’s very effective. If we can’t then he’s not able to exploit that. So it’s a work in progress.
“We can’t replace the blown diffuser obviously, but Sebastian was quick before they came along. It’s a re-learning curve.”
Meanwhile Newey says that he’s been hugely impressed by Daniel Ricciardo.
“He’s been right on it really from Day One. So often a relatively inexperienced driver coming to a new team, it takes a while to settle, and he seems to have adapted straight away to the new engine regulations and the slightly different characteristics of the car as a result of that. He’s been very good.”
Newey concedes that while the RB10 was closer to Mercedes in Monaco, that might not be the case in Canada.
“It was encouraging, but the circuit flattered us, let’s say, so it may not be the same at some of the circuits coming up. Montreal may not be our strongest circuit.”
Adam Cooper's F1 Blog 
Bit odd though – 4x champ takes a while to adapt to revised car. New driver ‘on it from day 1’ in new car & team. Surely Vettel’s not that much of a one-trick pony?
Looks like Seb is learning what it was like to be Mark Webber for all those years.
Except RBR wasn’t working flat out to develop the car to suit Mark like they are now for their golden boy. Mark was very vocal about not liking the handling of the car with the blown diffuser, & was often quicker than Seb when the throttle mapping & such was still being fine tuned, but they went full steam ahead, taking the car down a development path that suited Seb long before it yielded any results. Now here’s Dan doing very well, cruising in the car & beating finger boy, & here they go looking for his highness’ favorite driver aid again… & I’m betting that if Dan doesn’t like that setup, it’ll be tough luck to him. Sad, really.
Not only the car suiting the driver, but also how Seb’s car was usually flawless and Mark’s car was constantly having issues, especially with KERS.
There was no blown diffuser in 2013 and he did all right.
“RBR is trying to adjust the car to suit his style.”
They don’t need to “adjust the car to suit his style”. They simply need to give him a car as reliable as Ricciardo’s.
The amount of time they and Seb lost in testing is tough to make up, especially when you’re chasing down problems with an entirely new drivetrain.