Nick Heidfeld has admitted he has been surprised with the strong pace shown by his teammate Vitaly Petrov so far in 2011.
The German veteran admitted he had expected to easily beat the Russian based on his pace alongside Robert Kubica in 2010.
For this year, Heidfeld has replaced Renault's injured regular Kubica, with the pair knowing each other's strengths well following their almost four common seasons at BMW until 2009.
Asked if he therefore expected to easily outpace Petrov, Heidfeld told F1.com: "I had, to be honest.
"I think he has made some good improvements and I would assume that he is as good as the team hoped he would be," he added.
Niki Lauda said this week that Heidfeld is not compensating Renault for the loss of Kubica, but the 33-year-old German insists he is at least as good as his Polish successor.
"Some people will probably tell you that Robert was quicker, but there are also numerous others who will swear that I was quicker and if you look at the real numbers we've always been pretty equally matched," he insisted.