Heikki Kovalainen has said he was upset not to score points in the season-ending Brazilian Grand Prix – and that he thought it would be easier to come back and race competitively.

The Finn was drafted in by Lotus after Kimi Raikkonen opted to have surgery on his troublesome back. However, while much was expected from the 32-year-old, in the end he only finished 14th in Interlagos – the same result he took in the USA the week before.

Reflecting on the event in Sao Paulo, Kovalainen added a poor start was again the reason he didn’t do as well as he wanted.

“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. I think the car is great, but I was not able to unlock the pace and make the most of it,” he said.

“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.”

Despite the frustration, however, Kovalainen remains determined to return to the sport full-time in 2014, after spending most of this season on the sidelines, and he is expected to regain a race seat with Caterham.

“By the way, everyone who’s asking me to give up on F1 – I won’t,” he added defiantly via his official Twitter account, @H_Kovalainen.