Sebastian Vettel ended his first day behind the wheel of the SF15-T at the top of the timesheets in Jerez, while in contrast the man he replaced at Ferrari, Fernando Alonso, managed just six laps at his new team McLaren. Vettel finished half a second quicker than Mercedes' Nico Rosberg in third, an encouraging start for Ferrari despite headline times being of limited significance in testing. Marcus Ericsson's Sauber slotted into second after a late run on the soft tyre, ahead of Rosberg, who managed to accumulate a mammoth 157 laps – over two race distances of the Jerez circuit and more than double managed by anyone else. Rosberg had been top mid-way through the opening day of testing but Mercedes were able to focus on long runs in the afternoon and he dropped below Vettel and Ericsson in the final few hours of the day. The German's lap haulage is made all the more impressive by comparison to his rivals; Ericsson and Valtteri Bottas were the next closest with 73 each. He was beaten to the top of the chart by the 1:22.620 set by Vettel, who recovered from a slow start to record 60 laps of his own in the SF15-T. Alonso managed just six laps before lunch and McLaren soon reported a "niggly" problem was keeping the Spaniard in the garage. With just half an hour left in the session the team fired up its engine again but the MP4-30 did not emerge before the end of the first day. Daniel Ricciardo only added 13 laps to his morning total of 22 in the striking black and white testing livery revealed by Red Bull on Sunday morning. The team struggled with two issues, the first a battery issue which caused a rear brake failure through the MGU-K and another "engine-related" issue later on. However, Red Bull has already improved on last year's Jerez test where it completed just 22 laps in four days. Williams and Valtteri Bottas managed just five laps in the morning but enjoyed a more successful afternoon. Though only finishing fifth on the timing screens, Bottas completed a flurry of runs in the final few hours and managed to extend his and the team's mileage significantly. Ericsson's name sticks out at the top end of the timing screen but is proof headline times are of limited significance, with a late soft tyre run putting him in between Vettel and Rosberg. The Swede had triggered the first red flag of the 2015 season in the morning when he spun his Sauber on track. Toro Rosso rookie Carlos Sainz Jr caused a second in the afternoon after stopping in the middle sector, ending a day which saw him record his first 46 laps with the STR10. Only seven teams completed a timed lap in Jerez as Lotus failed to arrive in time for the first day. It was due to arrive on Sunday afternoon so should participate in the second day of testing, while Force India is missing the entire Jerez test in order to maximise development time before the Barcelona double header at the end of the month.