Despite what many would call an impressive first 11 races of his Mercedes career, Valtteri Bottas has described his performance as "average" so far claiming there is much more to come.

The Finn made an unexpected move to the German world champions in January, following the surprise retirement of world champion Nico Rosberg five days after winning the title in Abu Dhabi.

Though some were uncertain if he would be a match for Lewis Hamilton, the former Williams driver has calmed those fears with eight podiums, two wins and is still in title contention just 33 points behind current leader Sebastian Vettel.

"I was hoping to be slightly better positioned in the championship, and also as a team, I think," Bottas was quoted by Autosport as saying.

"I have work to do, there are still things I can improve, as long as I keep working with the team as we've been doing at this point of the year.

"I know the second half will be better for me, and my best performances are still on the way.

"I would say the first half has been average because I always set targets very high, but obviously [there have been] some good moments as well."

The 27-year-old also believes Mercedes feel the team's results have fallen shy of expectation as the domination of previous years has been replaced with a head-to-head duel with Ferrari.

"We are still looking good in the Constructors', but we have had some difficult races for us, which is not ideal," he said. "For us as a team, only winning is good enough, that's always got to be the target. I think we definitely have work to do."

On where most of that works lies, Bottas admits the weakness on aero-dependent circuits, which showed just before the summer break in Hungary, needs addressing if they are to be in certain contention.

"We need to work on our maximum-downforce package, that's the main thing," he commented. "There are still a lot of tracks to come that require a lot of downforce.

"Spa is more about efficiency, Monza is very low-downforce, then Singapore is about downforce again.

"We are really working hard and trying to get the car better, because if we don't make any progress, it's going to be a tricky season, for sure."