MARANELLO, Italy - Kimi Raikkonen, now 35, must prove in 2015 that he deserves to remain with Ferrari come 2016.Tha'is the warning from new Ferrari team boss Maurizio Arrivabene after recent reports that the Finnish driver wants to stay at Maranello not only next year but perhaps also in 2016.Raikkonen struggled through 2014, the first year of his return to the Maranello outfit from Lotus, with a points haul one-third the size of Fernando Alonso's and not a single podium appearance.PERFORMANCE DEPENDENT?Arrivabene was quoted by Finland's Turun Sanomat newspaper as saying: "The 2014 season was difficult for Kimi (Raikkonen) but that does not mean he has lost his speed. He's an F1 champion; more importantly. he won the title driving a Ferrari."I want to emphasise that Kimi needs to show he is capable. After that it will be possible to make a decision about the future."Raikkonen's team mate in 2015 will be his friend Sebastian Vettel, F1's quadruple consecutive champion for Red Bull from 2010-13."For sure," Arrivabene insisted, "drivers are not a problem for us."