Nico Hulkenberg has said that the challengers to Formula 1's top three teams have "a lot of work to do" to catch up.
Like other hopeful midfield teams including McLaren, Renault entered 2018 eager to be closer to the pace set by Mercedes, Ferrari and Red Bull.
Hulkenberg said that Renault can take positives away from Melbourne, but the bad news is "our deficit to the leaders".
"The guys ahead of us were a long way ahead," said the German driver.
"We wanted to reduce the gap in the winter, but it seems that it has grown even more. That is not good. We have a lot of work to do."
When asked where the midfield lacks pace to the front, Hulkenberg answered: "In my opinion it's everything.
"It's all about the little details. It's partly the engine, partly the aerodynamics, but also the chassis, the dynamics, the mechanicals, and so on."
However, he said that the good news is that Renault have started the season well.
"We have a good basis for further work," said Hulkenberg.
"Before [Romain] Grosjean and [Kevin] Magnussen went out, we were at their pace and also McLaren's. This year we have a good car at the beginning of the season."
The 2018 season continues in two weeks' time with the Bahrain Grand Prix.