Sam Michael was completely overloaded at Williams fulfulling many different roles. Williams and Head have even alluded to this in the past themselves. I thought that was common knowledge... apparently not. Another part of Williams' problems was engine related, another budget related. So to blame Williams' problems entirely on Michael is frankly bizarre. Jon Tomlinson, who also left at the end of 2011, was probably more key to outright car performance as chief aero guy, so he is equally if not more culpable, having been in charge from 2006 - the true start of the downfall.
Michael was (at the end) Technical Director at Williams - at McLaren he is sporting Director, the role Dave Ryan used to hold before he was sacked. They are two very different jobs! Michael used to be Frentzen's race engineer in 1999 at Jordan - Frentzen's best year in F1. If you actually bother to look at the jobs he held and when he held them, his record is pretty solid.
....and i'm gonna say this once only - chill the hell out guys before it is too late.
edit - Seems WB decided it was already too late!
