Renault number one driver Robert Kubica has blamed traffic for his failure to do no better than ninth in Sunday's F1 2010 Brazilian Grand Prix at Interlagos, the penultimate round of the season.

Kubica had qualified seventh in his Renault R30, but he slipped back in the race and conceded his car wasn't as good as the Williams of Nico Hulkenberg, who finished one spot in front in P8.

"It was a tough race this afternoon," Kubica said. "I spent every lap in traffic but I didn't have enough of a performance advantage over H?lkenberg to get past.

"I was losing a lot of time in the low-speed corners, and I couldn't use our top speed advantage because I was stuck on the rev limiter for a long time on the main straight, so couldn't attack him.

"The other critical part of the race came just after my pit stop, when H?lkenberg and I were running behind my team-mate for a number of laps and we couldn't make the most of our fresh tyres, which cost me a position to [Michael] Schumacher."

Team-mate Vitaly Petrov meanwhile, who had qualified well in tenth, had a poor start, which effectively ruined his afternoon. He eventually came home in 16th.

"I made a bad start and was in the middle of a big pack of cars in the first corner," he recalled. "I tried to give everybody space, then at turn two I took a normal line but had to take avoiding action to not hit [Jaime] Alguersuari and cause an accident. That put me on the kerb and I dropped to the back of the field by the time I exited turn three.

"After that, there was nothing I could do but try and push, do my normal race and make up positions wherever possible."

Renault boss Eric Boullier summed-up: "We knew that we would have a tough battle with the cars around us today, but we didn't take full advantage of our opportunities.

"Robert spent his entire afternoon in traffic and we weren't able to get him out of it with strategy, while Vitaly's race was essentially over on lap one. It's disappointing after showing good performance at different points of the weekend, but we will now focus on the final race of the season in Abu Dhabi, and on finishing our season on a stronger note."