Williams and Ferrari are poised to make a good start to the Formula One season after both finished winter testing with another strong showing on Sunday . Valtteri Bottas steered his Williams to the fastest time on the final of 12 days of preseason tests , with Ferrari 's Sebastian Vettel right behind him at the Barcelona-Catalunya circuit . Bottas clocked an early flying lap of 1 minute , 23.063 seconds . The Finnish driver and teammate Felipe Massa have consistently been among the fastest performers with both in the top two times through the final four days of testing . Valtteri Bottas clocked the fastest time for Williams on the final of 12 days of preseason tests on Sunday . Ferrari 's Sebastian Vettel and Sauber 's Felipe Nasr both trailed the Williams driver by less than one second . Vettel catches up with Nico Rosberg of Mercedes during day four of the final Formula One winter testing . Vettel and Sauber 's Felipe Nasr were both less than one second slower than Bottas . Nasr put in the most laps of the day with 159 in another promising ride by the newcomer . Whether a revamped Ferrari and confident Williams can challenge champion Mercedes is another issue . Nico Rosberg may have had a subdued final turn behind his Mercedes , but the German team has given no indication of slippage after dominating last season when Rosberg was Lewis Hamilton 's only challenger for the title . The Mercedes pair had set the pace on the previous two days , with Rosberg recording the fastest overall lap time in eight days at Montmelo of 1 minute , 22.792 seconds . Toro Rosso 's precocious Max Verstappen , who at 17 is the youngest F1 driver in history , again proved steady behind the wheel with the fourth fastest time . He was followed by Red Bull 's Daniel Ricciardo . Williams ' and Ferrari 's impressive displays during testing will give them confidence to challenge Mercedes . Next came Sergio Perez in his first turn behind Force India 's new car , right in front of Rosberg . McLaren 's Jenson Button , meanwhile , toiled to another session-low 30 laps after only managing two before the lunch break . McLaren has been in a mechanical muddle as it adjusts to its new Honda engines . It was also without driver Fernando Alonso for the final four days of testing while he recovers from a scary crash here last weekend . McLaren only managed to complete 380 laps this preseason . Compare that to Mercedes at 1,274 laps . Or Force India , which in only two and a half days , still racked up 365 . Lotus ' Pastor Maldonado was the day 's slowest driver , and the only one to end up in the barrier when he went off course at curve four . The Australian Grand Prix is in two weeks .
Williams driver Valtteri Bottas recorded the fastest time in the day 's tests . Ferrari 's Sebastian Vettel finished Sunday less than one second slower . The two teams will now look ahead to challenging Mercedes this season .