Toto Wolff admits Mercedes have had a terrible start to their season after experience issues on Friday and Saturday during winter testing in Bahrain. The team have seen their time on track reduced drastically after Valtteri Bottas experienced gearbox issues and Lewis Hamilton spun, forcing a red flag during Saturday's morning session. Wolff admits things aren't going as smoothly as they have in other years. "We are experiencing a terrible start, it is not like the other years," he told Sky Sport Italia. "We have reliability issues and we need to show what we can do." There were further eyebrows raised when Aston Martin's Sebastian Vettel experienced issues with his Mercedes gearbox on Saturday as well, but Wolff made it clear the problem isn't the same one Bottas had. "The gearbox problems between our car and Vettel's are not the same," Wolff added. "We have not adjusted the gearbox this winter and now there have been two problems with it and that of course sets the alarm bells off. "It is not good news, because it also costs us a lot of money and we have to pay attention to that too. [Lewis] Hamilton is not at all nervous, none of us at Mercedes are, but we have to learn to understand things. The balance of the car seems to be the big problem at the moment. "Red Bull have started like Mercedes has in recent years, they have made a Mercedes start and they are also faster than us these days.