The head coach in the NFL must be a strategist, a leader, a talent evaluator, a manager, and perhaps most importantly--a field marshall. By field marshall, I mean the person who sets gameday tactics, who sets play call doctrine, who manages the clock, and who decides whether to go for it or kick on 4th down.
At kickoff, a head coach is given a certain ability level in his team. During the game it is his job to squeeze every possible advantage from his team's capabilities, while minimizing its weaknesses. Part of his duties are to accurately assess the risks and rewards of every situation. His team is ahead 14-10 and it's 3rd down and 7 late in the 4th quarter. Should he decide to run and likely have to punt, but chew up some time and force his opponent to use a time out? Should he pass and go for the 1st down but risk stopping the clock, or even worse, an interception? The answers depend on how accurate his perception is of his offense's passing ability and his defense's ability to stop the opposition.
So given those abilities, how can we judge a head coach on his ability to make the best in-game decisions? Here is one way.
In the last post, I charted teams' expected wins vs. their actual wins. The model that estimated the expected wins had an r-squared of 0.85. This mean 85% of the variance in team wins could be accounted for by the model's variables. (If you're not a statistician, that means it's really good.) Some teams had steady expected wins from year to year, but had somewhat erratic actual wins. Some teams had expected and actual wins that matched up every year. But a couple teams stood out as unique.
In recent years, the Lions won fewer games than would be expected given their performance on the field. I admit part of that could be due to luck. However, such a consistent underperformance leads me to suspect something systematic is at work. Could it be that the Lions' coaching staff is not effectively maximizing its team's abilities? Is it inaccurately assessing the risks and rewards of in-game situations? What else would explain such consistent underperformance? Except for an abberation in 2003 (when they only broke even), Detroit annually won about 2 games less than expected.
In stark contrast to the Lions are the Patriots. New England has consistently won about 2 more games than we'd expect given their on-field performance. To me, this appears to be evidence of Bill Belichick's coaching skills, or at least his knack for in-game decision-making. He is known for some unconventional practices, such as going for it on 4th down in more situations than other coaches.
To truly assess a head coach's abilities, we need to follow the coach from year to year and from team to team. Using data from pro-football-reference.com, I collected modern head coach's wins and efficiency stats for each year since the 1982 strike. I chose 1983 as a starting point because it followed the birth of the "west coast offense" and significant changes in NFL rules governing the passing game (which actually began in 1978 but took serveral years for coaches to adapt.) I only considered coaches with 4 or more years of experience. In some cases I included some noteworthy coaches with shorter tenures such as Lovie Smith or Jim Mora Jr. I also included Spurrier and Saban (2 years each) because I was interested in how "big-name" college coaches fared.
I constructed a regression model similar to my previous efforts to estimate expected wins given each team's passing and running efficiencies on both sides of the ball. I propose that the difference between a coach's actual wins and expected wins are, to some degree, "extra" wins that a coach can squeeze from his team given a particular performance level. It is an estimate of his strategic and gameday coaching abilities. Each coach's "extra wins" are averaged and sorted from best to worst.
COACH "EXTRA" WINS/YR
Shula Don 0.73
Del Rio -0.29
Mora, Jr. -1.24
Shula David -1.40
The list ranks many of the more successful coaches at the top, and some of the least successful at the bottom. Shottenheimer, Gibbs, Reeves, Ditka, Shula are some of the legends at the top. The two coaches from last year's Super Bowl, Dungy and Smith, are at the top as well. Coaches with short and brutally unsuccessful tenures are at the bottom including Dave Campo, Butch Davis, Bruce Coslet, and Steve Spurrier. Some longer tenured coaches such as Ted Marchibroda and Norv Turner don't fare well either. I'm surprised to see top coaches such as Walsh and Cowher lumped in the middle.
But what happened to Belichick? He's down the list behind several other current coaches such as Billick, Reid, Fisher, and Lewis. It may be fair to break Belichick's head coaching career into two separate parts--at CLE and at NE. By his own admission he changed his approach following his time with the Browns, and applied what he learned since then into his current stint in NE. Belichick averaged -1.84 "extra" wins per season at CLE, but earned +2.33 "extra" wins per season at NE. The NE Belichick would be #1 on the list and the CLE Belichick would be third from the bottom. I might attribute such a difference to the small sample size (3 years) at CLE, but such a stark difference speaks for itself.
To be fair to other coaches with distinct tenures, I split the averages of some other notable coaches apart too. Redskins fans may not like what they see.
Gibbs ('83-'92) 2.11
Ditka CHI 1.37
Shottenhmr CLE -0.11
Parcells NYG -0.36
Reeves DEN 1.85
Note: Also, since this post is appearing on many other sites recently, I've posted a response to many of the excellent comments and criticisms over the past several months.