I don't know if anyone saw the "development special" on Sky last night, but they had an ex-Ferrari engineer on there who had an interesting theory about Ferrari's and Sauber's pace. Given that it was Ferrari who instigated the whole business about not having to homologate their engine before the start of the season, he speculated that they might still be running their 2014 engine, or a lightly modified version, and were therefore able to run it at full power, while Mercedes would have been more cautious for the first test with a brand new motor.