You can't begin to compare Rodgers, Martínez and Lambert with sherwood, shearer and Adams.
We ve also hired proven managers in the past. Obviously the more proven, the higher the chance of success but they have also failed.
It's about the right fit.
Yep, being provne just increases the chance of successful - no guarantee obviously but at least they know what it takes to win. Hiring an unproven manager is more of a gamble
Agree with the fit comment but for me, first thing is you work out which proven manager's are available and then narrow it down by fit (ie right type of football, managed in DoF structure before, native or near native english etc etc)