It's easy to look at coaching candidates and assume that the success of the unit they coach is a direct indication of their coaching abilities. A perfect example is Jaguars defensive line coach Joe Cullen who went from a fan favorite to a seemingly easy loss for the team after the 2012 Jaguars finished last in the NFL in sacks.
Sure, finishing last in sacks would seem to indicate that Cullen didn't do much with the team, and that's why you won't see me writing him an ode if he is employed elsewhere in 2013. However, it would be an entirely different story if the Jaguars finished last in the NFL with pass rushing personnel like the Broncos or Rams.
Correlation doesn't mean causation.
Former Jaguars offensive coordinator Dirk Koetter and former head coach Jack Del Rio had plenty of success in 2012 with units that had much more talent than they had to work with in Jacksonville. It all leads you to point back to the old Vic Ketchman adage "players, not plays."
But if that was entirely the case, then what's the point of a search for a head coach? Obviously some are better than others or else the entire point of searching for a head coach would be moot and anybody could be appointed to the position as long as they are given talented enough players to work with.
A head coach must be able to succeed in a much more managerial position than that of a coordinator and should be able to make players better under his coaching. How are those criteria quantified in the records and statistics? They're not. It can't be done and it makes the search for a coach a difficult one.
Yes, Greg Roman's offense in San Francisco has been impressive and blew away the Green Bay Packers in the playoffs last week, but how much of a role does Jim Harbaugh play and would the team be good if it didn't have the players that has made the running game so strong for the 49ers?
None of Brian Schottenheimer's offenses have been particularly impressive during his time as a coordinator for the Jets and Rams, but how much did Chad Pennington, Mark Sanchez and Sam Bradford factor into that, and can the offensive collapse of Sanchez and the Jets in 2012 be at all attributed to the loss of Schottenheimer?
They aren't questions that can be definitively answered with numbers or records. They are also the reason why I don't have a favorite candidate for the Jaguars head coaching vacancy. I'm perfectly content with General Manager Dave Caldwell talking with each of the candidates and I'm certainly ok with letting him play the role of clairvoyant.