Sebastian Vettel's Thursday headline time was impressive and I can confidently predict it won't be beaten by Mercedes this week. Why? The team tells me it has not selected any hyper-soft tyres -- the newly-introduced softest tyre in Pirelli's range -- with them to testing, because it is never going to be used at May's Spanish Grand Prix here. Teams make their own selections based on the data they wish to gather from these tests. That prevents us from having the chance to make a like-for-like comparison at the end of the test, however ambiguous those can be, and means we will have to make do with the ultra-soft lap times set by Lewis Hamilton and Valtteri Bottas.