Mercedes boss Toto Wolff has admitted he did "worry" about the team's pre-testing troubles in Bahrain, but hopes they have found the "hair in the soup".
Champions Mercedes were hit by a gearbox problem on the opening day that limited track time.
Seven-time world champion Lewis Hamilton, who spun into the gravel on Saturday and brought out red flags, and Finnish team-mate Valtteri Bottas both said the car's handling needed improving.
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"I always worry, sometimes for the right reasons, sometimes for the wrong reasons," Wolff told Formula One television.
"Pre-season testing is always exciting because you always find the hair in the soup, things that are not good."
The Austrian defended his team's decision not to carry out a filming day 'shakedown' of the new car before testing started, and said there was no complacency.
"The shakedown if done in the right conditions allows you to understand a little bit more but our failures in the first days were not down to doing or not doing a shakedown," he said.
"We will crunch the data, try to understand where we performed well and where not, where we had good correlation to our simulations in the (wind) tunnel and where not.
"It's like sleeping overnight on an idea. The next day you wake up more intelligent."
Mercedes have won the last seven drivers' and constructors' titles, an unprecedented feat, but completed fewer laps in testing than rivals.
The season starts in Bahrain on March 28.
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