Dietrich Mateschitz has spent over a billion dollars on RBR, yet people think he's going to let the key to his teams success be headhunted away because he's not willing to pay him an extra 10-20 million a year?
McLaren made a faster car than Newey in 2012 and wasted the opportunity. Mercedes now have made a better car than Newey. Byrne was designing cars at Ferrari when Ferrari rubbished all in front of them. McLaren in 2012 couldn't get their act as a team together. You knew something was wonky... come to think of it, it seems things aren't exactly how they should be between Hamilton and garage (going by today's race and radio messages), but i think if there's one thing Hamilton learned from Alonso in 2007 and his own examples in 2012 is to potentially keep his trap more shut than before.
F1 in modern times has been more of team sport than it ever was, as margins everywhere have shrunk. Ferrari won many races as McLaren couldn't sort their act in the pit-lane. Infact they tuned pit-stops into a fine art. It was so brutally effective, that it is bye-bye refuelling . Did i mention that McLaren and at times others turned up with cars which were potentially faster than Ferrari overall and yet they went home with no silverware?
It is funny how people think hiring an aerodynamicist will solve all ills, especially if his last name is Newey. No one looks back and wonder why Newey won absolutely nothing since 2000-2010. You need more than just one man to get it right nowadays.
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As someone already said... power unit is a big difference maker. RBR are suffering for it, and so are Ferrari. Having Newey and Byrne (jizzed pants dreaming of concepts and engineering solutions... yes i'm a nerd) will definitely add value, but that is not everything.