The combined timesheet from the final test of the 2011 pre-season makes interesting reading just over a week before the season begins.
With Mercedes' admittedly "basic" launch car finally fully updated, it was seven time world champion Michael Schumacher leading the charts.
Brawn told the Frankfurter Allgemeine newspaper.
The Briton admits he had felt "nervous" when the W02 was a second off the pace and so much was riding on the major Barcelona upgrade.
"It was hard to keep calm, and I was constantly reminding the team to stick to the plan. In situations like that, it's tempting to react and waste resources," said Brawn.
Schumacher told El Pais newspaper: "All I can say is that we finally found the right balance and the aerodynamic package works. As for whether we will be in front in Australia, I don't know."
With the second best lap of the Circuit de Catalunya last week was Ferrari's Fernando Alonso, ahead of Sergio Perez in the impressive Sauber.
The fastest Red Bull (5th) was Sebastian Vettel, with Mark Webber just eleventh best.
It was hard to keep calm.
"Throughout my career," said veteran Rubens Barrichello, "I have never seen a pre-season that is so difficult to interpret.
Also with notably good laps in Barcelona were Renault and Toro Rosso, while the best McLaren driver was Lewis Hamilton in just fourteenth place.
Heikki Kovalainen's Lotus, meanwhile, was faster than either of the Force India drivers, while in the absence of Timo Glock, rookie Jerome d'Ambrosio brought up the timesheets in the sluggish new Virgin.