Sebastian Vettel admits he is simply "missing something" as he struggles with this year's Ferrari.

The four-time world champion currently sits 13th in the Drivers' Championship on just 18 points after 13 races, less than a quarter of the 75 accumulated by teammate Charles Leclerc.

Last weekend at Portimao, Vettel conceded the Monegasque simply had a better grasp of the SF1000 than he did, but, despite only have five races left at Ferrari, insists he is still pushing as normal.

“Just like any time throughout my career, I'm [trying] to do everything I can to go as fast as I can, but currently, obviously, I'm not able to get the same out of the car as Charles is," he told Formula1.com.

"So obviously, I'm looking forward, with the engineers, to try and understand and work on it, and continue to work on it.”

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It is well-known that Vettel favours a car with a stable rear, something this year's Ferrari certainly doesn't have, but still the 33-year-old is baffled by his inability to improve.

“So far in my racing life, I've always been able to extract the maximum,” he said. “This year seems a bit different but there's no other choice than working on myself and working on the car.

“I don't think it's down to the way the car is handling, I think you always have to adapt,” he added.

“I think that's true in go-karts all the way to Formula 1, and it's something that normally has never been a problem. But clearly, as I said, I'm missing something this year and I'm trying everything I can to get on top of it.”

Ferrari boss Mattia Binotto defended Vettel's performance, however, insisting he and Leclerc were not night and day apart.

“I don't think there is a key difference,” he commented. “I think in the end it's very small differences. We're not speaking about a big number, it's always a sum of hundredths per corner, per braking, so it's very little.

“As Seb said, certainly it's a matter of feeling, it's a matter of feeling the grip, it's a matter of extracting the potential.

"And it's our task, our duty, to help him, to support him in a way that he can deliver better, and that's it. But looking at the data, there are no big differences, that's the point.”