Declaring McLaren to be "50 percent behind" schedule, Eric Boullier admits development is taking preference over performance at this stage.
Friday's running at the Circuit de Barcelona-Catalunya proved to be McLaren-Honda's most successful day to date with the new package.
Fernando Alonso managed 59 laps with a best time of 1:25.961, which put him 1.387s off the pace set by Red Bull's Daniel Ricciardo.
Reliability, though, continues to hamper the team as Alonso's 59 laps meant he completed the fewest of the ten drivers out on track.
"We did maybe 50 percent of what we wanted to do," Boullier told motorsport.com.
"We have 12 days to get ready, so if we miss half then we won't be ready 100 per cent. So our development – in terms of plan – we are 50 percent behind."
The Racing Director added that McLaren have yet to switch their focus to performance with the new car but rather are still focusing on ensuring it all works as expected.
"We are not obviously looking for performance," he added. "The expectation of what we wanted to build, it looks like we achieved it so far. Next week there should be some more parts.
"We have a lot of systems to check, that includes a lot parameters to understand the car. We have to do a lot of mileage, to gather data, before we concentrate on performance. The priority is the development programme.
"The car is still in launch configuration. We couldn't put enough miles now to bring some more parts.
"Next week we'll see another step, and then in Australia we'll see another big step."