Robert Kubica has finished in the top five in three of this season's four races
Renault's Robert Kubica has warned his team it will be difficult to continue their impressive start to the season as their rivals improve their cars.
Renault have picked up 46 points in 2010, but they do not have any major upgrades for the Spanish Grand Prix.
"It is important to remain realistic, we still need some big steps to be at the front of the grid," said Kubica.
"Maybe the order of the teams will be quite different compared to the start of the year," added the 25-year-old.
Kubica is currently seventh in the drivers' championship with 40 points, 20 behind leader Jenson Button, but the Polish star is aware that the competition is likely to have made major improvements in the three-week break since the Chinese Grand Prix .
"The next race in Barcelona will be another big test for us because the return to Europe is usually a turning point in the season with many teams planning big upgrades to their cars," said Kubica.
"A lot of the teams have big expectations for their new packages, but we are not planning to bring any huge updates.
"We will keep gradually improving the car, just like we did during the first four races.
"We have to wait and see how we compare with the others."
Despite sounding a note of caution ahead of this weekend's first European race of the season, Kubica, who joined from BMW at the end of 2009, expressed his delight at the start he has made to his Renault career.
"I think we should take a lot of positives from the first four races," he said.
"If you had said to me at the start of the season, or even after Bahrain, I would have scored 40 points and three top-five finishes, I would have been more than happy.
"However, at the same time there has still been some frustration, especially in Shanghai where the safety car in the middle of the race definitely cost me a podium.
"But you have to accept that this is part of racing. Sometimes the luck goes your way and sometimes against you."