Courtesy of bitter Chicago fans over on Football Outsiders, I went on a hunt to see what the numbers said about the offensive work of one Mike Martz, Sooper Genius, over the years. Everything I collected I left over there in the current Audibles thread if you're curious to see the "detailed" work so far.
Here's the short version: the success of the Martz's offense seems to be, on a first look-over, almost directly tied to the quality of the team's offensive line, particularly run-blocking. It's hard to get good numbers: it's a thing measured best and perhaps only by things like FO's ALY and Advanced NFL Stats' WPA applied to the line.
This may be just a fact of football: no line, no offense. On the other hand, teams like Green Bay and Detroit have spent this year at least trying to disprove the hypothesis. My initial thinking is that there is enough lack of correlation in general to make the huge correlation in the case of Martz's offense, at St. Louis particularly, noteworthy.
As implied by the title of the post, 2002 seems to have been the edge of the waterfall for the Greatest Show on Turf. From 1999-2001, no team put up better total numbers, even when evaluated by modern advanced stats. Then in 2002, most of the advanced rankings drop the team's ranking to the 20s (out of 32), where the Rams stayed for the next three years until they fired Martz and the Lions picked him up. Ever since then, Martz's offense has been producing more of those rankings-in-the-20s, seemingly without any regard to the quarterback involved (though possibly had Cutler stayed healthy we would have seen something different in Chicago this year).
As I mentioned, the key seems to be the offensive line, judging by ratings; but what I can't figure out is what went wrong in St Louis in 2002. The line had only one change; the lineman lost at right tackle went on to "anchor" a mediocre Browns' line for years. But that seems an improbable cause, by itself, of such a huge decline. Anyway, there is a mystery here which I am tempted to research further.
(It could of course be much simpler: Martz hasn't had a stable quarterback situation since 2001 except the 2004 season which was much better; and then Chicago, though last year seems a little weird. Anyway...)