Heikki Kovalainen says he is to blame for failing to score a point at the Brazilian Grand Prix.
Kovalainen, who was replacing compatriot Kimi Raikkonen, finished the race in 14th place.
"It has been a great opportunity to drive for Lotus F1 Team and I’m upset that I was not able to score any points for them today," he said.
"I think the car is great, but I was not able to unlock the pace and make the most of it. I made some mistakes – probably through lack of routine – but I was anticipating it would be easier to come back and race competitively."
"My starts both here and in Austin were really poor, with procedural issues both times meaning I wasn’t able to keep pace with everyone off the line. That was disappointing as it’s such a big part of the race and it’s very difficult to recover positions. I’d like to thank everyone at Lotus F1 Team for all their support during these two races."
Team-mate Romain Grosjean exited the race early when his engine failed on the third lap.
"At this point in the season I think everyone needs a holiday, but apparently my engine decided to go on vacation early!"
"Of course, that’s not the way we wanted to end the year but it’s been a fantastic season for the team and I think we can be really proud of what we’ve achieved together."
"We’ve proven this year that we are a top team, and I’m certainly proud of all the guys in the garage and back at Enstone. Today was obviously disappointing for everyone as they deserved more from this final race after all their hard work, but now it’s time to get a little bit of rest and then focus on making sure we head into 2014 and the new regulations as one of the top teams once again."