George Russell has urged Mercedes to use its "limitations" from the first pre-season test and "optimise" the W13 ready for the Bahrain Grand Prix.
The Silver Arrows topped the timesheet with a one-two, with Russell narrowly behind team-mate Lewis Hamilton who set a late flurry of fast laps on the final day in Barcelona.
Russell had suggested that McLaren and Ferrari were ahead on true performance given the average team simulations measured across various predicted fuel loads, power modes and tyre compounds.
With F1's radically different regulations in their infancy, teams are expected to turn up to the second test in Bahrain with upgrades and refinements.
Asked how different the W13 would be, Russell replied: "We will see with all of the teams. We have got this massive regulation change and we all arrived in Barcelona with our best estimate of where we needed to place the car.
"But obviously there were a lot of things on track that were quite different to what some people may have expected.
"So we need to go away and try to optimise from the limitations we had. We will see some changes come Bahrain and throughout the season.
"I am sure the development is going to be pretty rapid for everyone. Whoever can get on top of that the quickest or most efficiently will be the ones on top come the end of the season."
The second three-day test gets underway on March 10, with the first race also in Bahrain a week later.