Mercedes' Toto Wolff has down played reports that his team are the clear 2014 favourite after the first winter test at Jerez in January 2014.Speaking to Motorpasion, Wolff said: "It is too early to know. It is just testing and so you can't say much. It was good that we were able to do so many kilometres, Nico Rosberg even did a race simulation, which is something the others were not able to do.MORE CHANGESOnly in Australia will we see something representative. The cars are going to change a lot until then, there is a lot more testing to do."Rosberg agrees that, while Mercedes had a successful test in southern Spain with good reliability, "a lot of work" still lies ahead before Melbourne.Rosberg said: "Performance-wise we don't know where we are because you can't really compare to the other cars, but that's not the focus right now."Teammate Lewis Hamilton added: "It's a bit early to say this definitely, but right now the car feels pretty good. So far so good; now we just have to continue working hard and see what happens in Bahrain."