SAKHIR, Bahrain - Mercedes continued to set the pace on the fourth and final day of the second 2104 pre-season test in Bahrain on Saturday (Feb 22).Nico Rosberg posted the fastest time overall and champion team Red Bull had more problems.KIMI CRASHESRosberg topped the timesheet with a lap of 1min 33.283 seconds, a second quicker than British team mate Lewis Hamilton managed on Friday (Feb 2), as Rosberg completed 89 laps at the Sakhir circuit.McLaren's Jenson Button went second quickest 1.5 seconds behind Rosberg, while Ferrari's Kimi Raikkonen was third as he ended his day five minutes early following a late crash that ripped the front nose off his car.'WASN'T A GREAT DAY' Brazil's Felipe Nasr, who was announced as a test and reserve driver for Williams, went fourth quickest on the day producing 87 laps.Rodberg said: "It's been a good day we were doing lower-fuel stuff in the morning, really getting into the qually rhythm and finding a balance for that. I felt comfortable in the car - it's important for me to feel at home, that everything is to my liking."Red Bull, winner of the 2013 Drivers' and Constructors' titles with Sebastian Vettel, had another problematic day as its pre-season campaign continued to flounder.Daniel Ricciardo, pulled from the track after only 28 laps, completed only 15 on Saturday (Feb 23) due to a power-unit problem with the Renault-powered RB10. In total, Red Bull has registered only 137 pre-season laps against the 624 of Mercedes, 541 of McLaren and 538 of Ferrari.Ricciardo admitted: "In all honesty it wasn't a great day. I guess we still need more time. We have four more days coming up - I hope to maximise those. On the run we did today the car did feel better but another problem arose and we couldn't exploit that potential."Overall, Mercedes registered the top two times of the second pre-season test followed by the McLaren's of Button and Kevin Magnussen.Teams will remain in Bahrain for the third and final pre-season test which will start on Thursday (Feb 28) and last four days.