Heikki Kovalainen expects the Caterham F1 team to jump ahead of 'division three' rival Marussia once it bolts on its first major upgrade of the 2013 season.

The Finn, who will once again drive the CT-03 in free practice at this weekend's Spanish Grand Prix, has admitted that the car was more difficult to drive than last year's - which he raced throughout the season - but is confident that the raft of development parts destined to appear in Barcelona should make a decisive difference in the back-of-the-grid battle.

With only minor tweaks made to the 2013 car over the opening 'flyaway' rounds in Australia, Malaysia, China and Bahrain, Charles Pic finally ended Jules Bianchi's hold over the rivalry in Sakhir, and Kovalainen is looking forward to helping the Frenchman - and team-mate Giedo van der Garde - move further ahead this weekend.

"I could feel that the car is more difficult to drive than it was at the end of last year," the Finn told Sky Sports, "Of course, the tyres have changed, and the set-up has changed as a result, and [it is] mainly because of these two things the car has become a bit more difficult to drive.

"On the other hand, I could feel there was more we could use in this car and I felt that, after driving the car, we should [already] be able to beat Marussia. Now, with the updates coming, we should be in a position to beat them."

Ironically, there was a time when Kovalainen might have been on the other side of the battle-line, having been rumoured as a potential replacement for Luiz Razia, when the Brazilian's sponsorship failed to materialise. The seat alongside rookie Max Chilton eventually went to fellow newcomer Bianchi, but Kovalainen - who also dismissed speculation of a feud with Caterham boss Tony Fernandes - insists that he was never a serious contender for the Marussia ride.

"I didn't actually actively talk to other teams," he claimed, "I talked to Caterham for quite a long time, right up until they announced [van der Garde] and never really held any serious talks with anyone else."

The Finn's appearance in the Caterham pit at Sepang set tongues wagging about a potential comeback and, having initially brushed the talk off by claiming that he was merely taking advantage of Fernandes' Malaysian hospitality, Kovalainen now admits that he was already discussing the future with his former employer.

"At some point [during] the Australian Grand Prix qualifying, I sent a message to Tony and said 'I would have been in Q2'," he revealed, "We started discussions about it again and he said 'would you like to come and test our car'."

Kovalainen will replace van der Garde in the second Caterham during FP1 at the Circuit de Catalunya this weekend, but is thought to have already had a run with the new development package, having taken the wheel of the CT-03 during a recent 'filming day' at Magny-Cours in France. Despite heavy rain, the Finn was photographed running a visually different Caterham which, amongst other things, featured a reworked nose treatment, ridding the car of the ugly step with which it contested the opening four races.