Lotus are adopting a "wait and see" policy over Mercedes' pace following the Brackley squad's good showing during testing.
Nico Rosberg posted the fastest time in Barcelona during pre-season testing this year as his 1:20.130 was more than good enough to help to finish top on Sunday while his team-mate Lewis Hamilton was quickest on two of the other three days.
Despite the W04's impressive pace, Lotus team principal Eric Boullier won't lose any sleep over their rivals' performances ahead of the opening race of the year in Australia.
"I'm not saying we're confident, but it's not a worry," he said.
"I think they've definitely improved. But if you remember last year they were competitive at the beginning of the season as well. So there is no reason why they would not be competitive again at the beginning of the season, so let's wait and see in Melbourne."
Rosberg and Hamilton had plenty of qualifying practice during the test at the Circuit de Catalunya and Boullier believes it is hard to distinguish who actually showed their true pace.
"There is a big challenge to see what is going on because there was one-lap performance from some teams and especially the Mercedes car was fast, definitely," he added.
"Then you have a different story when you go for higher fuel and the race simulation. I think the [one-lap] performance order will be different to the order in the race, so that's going to be interesting.
"But there is still a question mark about the tyres. Obviously the conditions are a bit different compared to what the tyres have been designed for. I think with hot temperature at coming races it's going to be different behaviour."
Lotus have had a solid pre-season and the team are hopeful that Kimi Raikkonen and Romain Grosjean will be challenging for top honours at most races.
"Kimi towards the end of the season was delivering a lot more in qualifying than at the beginning and I think both drivers are going to be ready from race one and a better fit and in better race condition than last year," he said.
"So we should be able, as a team, to deliver more from race one. So yes I hope to be chasing and fighting for the top positions."
