Nick Heidfeld didn't deliver speed or leadership, says Renault team principal

Strongly dismissing any suggestions that Bruno Senna was drafted in because of any sponsorship possibilities his appointment could bring, Boullier said that he felt Renault's troubled 2011 campaign needed a 'shake-up' - and changing drivers would help achieve that.

"We reviewed our performance and our level of motivation, a lot of things through the summertime, and I had to take some decision to clearly show some new direction," said Boullier when asked by AUTOSPORT to explain the driver change.

"There was an opportunity as well to assess Bruno as a driver, and this is why we moved on."

He added: "Nick is a nice guy, but I think something did not work. His leadership didn't work in the team and when you are sometimes slower than Vitaly, in fact most of the time slower than Vitaly, it is difficult for him to push the team and to settle himself as the team leader.

"In the end if you talk about management, not just speed, when you have the negative spin starting, the negative loop, it is complicated to stop it.

"I don't say the performance of the team was because of Nick. The car is not good enough, we have not developed the car well enough, we made mistakes as well - but the loop is negative. So I had to change something in the team and I had to change some things with the drivers as well to shake up and wake up everybody. I need to bring this motivation back to make sure that we can shake up everything, and it is not easy."

Boullier confirmed that the plan is for Senna to see out the season at Renault, but that cannot be confirmed prior to a court hearing that will rule on Heidfeld's claim of a breach of contract, which is due to be heard in London on September 19.

He also expressed some surprise that Heidfeld had chosen to appear at the Belgian GP, where he was dressed in Renault team clothing and spent time in the team's garages and motorhome.

"Yes, a little bit," said Boullier. "Obviously I guess he does not want to put himself in a breach situation, this is why. So as long as he keeps putting himself in a position to promote the team, and not telling anything else, then I am fine."

Read the full interview with Eric Boullier here.