Formula 1's first pre-season test highlighted that McLaren continues to lack performance despite improvements made by power-unit supplier Honda, according to racing director Eric Boullier.
McLaren enjoyed a positive start to last week's Barcelona test, completing 248 laps over the first two-and-a-half days.
Over the remaining day-and-a-half, however, it managed just nine as a hydraulic leak brought Jenson Button's Wednesday to an early end, while a hard-to-find coolant leak wrecked Fernando Alonso's running on Thursday.
But there were some positive signs, with Honda appearing to have made progress with its troublesome ERS.
Speaking to Autosport, Boullier said: "They have definitely fixed the main issue we had last year, which was deployment.
"However, we are still not at the performance level of Mercedes and Ferrari, so there is still a lot of work to do.
"But after the problems of last year, the week was more about making sure we could run, with so much to check on the car, to get out of the car and to send back to the factory.
"From the end of last season in November through to the start of the test all we have been able to work on is simulation.
"That means you tend to deviate all the time from the truth, so now the truth is coming back into the system.
"That allows us to ensure the correlation is OK, and we know where we are and where we are going.
"[The second test] will be interesting because everyone will have to do race simulation and qualifying runs at some stage, so then we will start to pick things up."
After finishing a miserable 2015 ninth in the constructors' championship on Honda's return, Boullier has one aim this season - rapid progress.
"McLaren is all about winning, so if we are not winning then we are failing," he added.
"That's the theory, so then we have to put everything in place to be winning.
"As long as we then have a good chunk of progress in the right way, and the speed we catch up is much, much higher than others, then that means we are on the right path.
"For this season it doesn't have to be wins, it doesn't have to be podiums, that might be too much too soon.
"The wrong thing is to draw the wrong expectations. We can't raise expectations too high otherwise we fall flat."
Follow Formula 1's second and final pre-season test at Barcelona live from 7:30am on Tuesday with Autosport Live