Valtteri Bottas admits he is enduring the most difficult spell of his career after another disappointing weekend in Malaysia.

The Finn was a real title contender prior to the summer break, but has fallen 59 points behind team-mate Lewis Hamilton after a barren sequence of races.

Bottas finished fifth in Sepang, crossing the line more than 40 seconds behind Hamilton, and confessed after the race that he needs to up his game.

"Being honest it may be the most difficult time of my career so far, in terms of how I feel every time I get in the car," he said. 

"I just want to perform, to be on a good level, but I haven't been doing this for some time for various reasons.

"I definitely want to turn it around quickly. If I keep doing races like this then that's no good for anyone.

"The team needs the points, I need the points, and I want the points. I want to do much better than this.

"I want to turn it around quickly and do whatever we need to do it. But there are still many question marks."

Bottas says his confidence has taken a knock amidst the slump and he no longer feels totally comfortable behind the wheel.

"After such a bad run of races just pure confidence in the car and trusting your own skills and being 100 percent comfortable makes a massive difference.

"This weekend I haven't been 100 percent comfortable.

"It's never a good thing when you jump in the car and you don't feel 100 percent secure and if you don't know that you can be the absolute quickest that is never good."

The 28-year-old says a change in mentality could be key to turning his fortunes around.

"You need to get that back and need to get that feeling of enjoying the driving and letting yourself a bit looser," he explained.

"But it comes from understanding all those fine details when you are struggling sometimes.

"This sport is so sensitive to the mental state of a driver. You need to be absolutely on it if you want to be at your best."