Kubica stays realistic on title chances

The Pole moved into the lead of the championship after scoring his and his team's maiden Formula One victory at the Canadian Grand Prix.

After the first seven races of the season, Kubica is four points ahead of McLaren's Lewis Hamilton and Ferrari's Felipe Massa.

But the BMW driver believes defending his position will not be easy at all.

"For sure it's very nice to be the championship leader after seven races, but you win the championship when you are the leader after 18 races," Kubica told reporters during testing in Barcelona.

"Of course it's a good feeling but I think it will be difficult to defend this position.

"Realistically speaking, we are missing a bit of performance to Ferrari and McLaren."

Kubica said the victory will not change his approach to the races.

"After the race I analyse what happened and what could have gone better and what we can improve, and that's all. We are looking forward to the future and the next races. That's the most important," he said.

The Pole admitted the last 20 laps of the Montreal race were "boring", despite the danger of making a mistake.

"They were quite boring laps, because in the end I had a very good pace, but in Montreal the track conditions were very difficult and if you went 10 centimeters off line it was very slippery and very easy to make a mistake.

"So it was very important to keep the concentration and bring the car home without mistakes."