The Finn, team-mate to five-times world champion Lewis Hamilton at Mercedes, gave his assessment on the final day of the first four-day pre-season test at Barcelona’s Circuit de Catalunya.
Ferrari was fastest on the first two days and the Italians also covered an impressive amount of mileage in the new SF90 car while Mercedes has been working through its programme without setting any eye-catching times.
Bottas said the cars would be very different by the time of the Melbourne race on March 17 and Mercedes had new parts coming before then. He warned, however, that even with the upgrades Mercedes still needed to make the car better and quicker, with work to do on the balance.
“It feels a little bit different (to last year), at least in these (winter) conditions,” he said.
“It seems to be again, with the tyres, quite a narrow window to get them to work.
“It seems like balance-wise a little bit on a knife-edge at the moment too. But there’s nothing fundamentally wrong, we feel. I think there is a lot of potential but it is not yet quite there.”
Mercedes has said it intends to focus more on speed and performance when performing tests after concentrating primarily on reliability until now.
Hamilton also recognised Ferrari was quick when he spoke to reporters but said that was the case in testing last year and Mercedes prevailed in the end. Mercedes chases its sixth trophy this year. Ferrari last won a constructors’ championship in 2008.