When Green Bay Packers head coach Mike McCarthy abdicated his play calling on offense to associate head coach Tom Clements this off-season, discussions exploded. 

Specifically, speculation ran rampant as to whether Clements would truly have his hand in the offense. Would he be more so a puppet and quarterback Aaron Rodgers would really be the play caller? Or, would Clements be calling all plays and have a different style and result compare to McCarthy? What would the overall impact be to the offense? Will things get better, worse, or stay the same?

It's recently been revealed that Rodgers will not in fact be calling the plays and Clements will be in charge of the play sheet. Rodgers himself said so. We can put that argument to rest for now, although I'm sure Rodgers will still have plenty of audible power at the line of scrimmage, but that's another topic altogether.

Now is a great time to revisit the question of whether or not play calling is overrated. This is an age-old discussion that one side says it's overrated and all comes down to execution. Any properly executed play will move the sticks and keep the drive going. The play call itself doesn't matter, but the guys on the field running the play do matter.

In contrast, the counter argument says football is the ultimate chess match, and the ball can only be moved when the play call is right. Calling a play at the right time is everything; sending in the wrong play at the wrong time is disastrous. In other words, situational football is more important than total execution and the players on the field. Remember Charlie Weis and his so-called "decided schematic advantage?"

Let's have a little fun and dig into some numbers to see if we can elucidate an answer to this debate while also shedding some light on what we can expect with the play calling change for the 2015 Packers season.

To complete this exercise, we'll look at the offensive statistics from when Mike Sherman (2000-2005) and Mike McCarthy (2006-2014) called plays. Both coaches ran the "west coast offense." Yes, myriad differences exist within each implementation, but they are similar enough in my mind to make a valid comparison. Furthermore, both head coaches had Hall of Fame quarterbacks (Rodgers is at a Hall of Fame pace) at their disposal, so it's not like comparing Jay Cutler or T.J. Rubley to Peyton Manning or Tom Brady.

This should be a neat comparison because, as a reminder, Sherman was sequentially fired by the Packers and Texas A&M as head coach, and then by the Miami Dolphins as offensive coordinator. In his time in the NFL, he had several winning seasons, but he never won a Super Bowl and often had early exits from the playoffs. He recently accepted a position to be a high school head coach of all places, signifying his fall from the top, no matter how well his intentions are in this most recent case.

In contrast, McCarthy is often hailed as an offensive genius and has won a Super Bowl. Therefore, we should be able to see if play calling truly matters when comparing men of different public opinions and resumes.

Below are tables of offensive statistics from each coaching regime. All statistics are courtesy of www.pro-football-reference.com.

Null: Play Calling is Overrated

When comparing the statistics compiled by both coaches, we have to assume a null hypothesis. In this case, the null hypothesis says there is no difference between the coaches. If that is true, that must mean that play calling is overrated. In other words, almost anyone can do it and it's more about execution. 

On the surface, it appears that McCarthy's offense ranked higher than Sherman's in both scoring (6.6 to 8.8) and total offense (6.6 to 9.8). Also, it averaged more total yards (5957.4 to 5602.8) and passing yards (4194.2 to 3755.0), but averaged fewer rushing yards (1763.2 to 1847.8).

However, are those significant differences?

To determine any significant differences, we'll look at two-tailed, two-sample t-tests for independent means at significance 0.05 (if the P-value is less than 0.05, there is a signficant difference). Then, we'll follow that analysis with a MANOVA, which is a more robust multivariate test that is even more sensitive to differences between the coaches and assesses the complete body of work in addition to each statistical category separately (if the P-value is less than 0.05, there is a signficant difference). 

Results

When looking at the statistics from both tests, the only difference between McCarthy and Sherman was in passing yards. The tables above show that we have failed to reject the null 4 out of 5 times for each test, which shows that there is virtually no difference between offensive statistics for both coaches.

Additionally, when combining all variables, MANOVA showed there was no difference between the coaches overall. The body of work between coaches is not statistically different from each other.

Therefore, play calling appears to have no statistical effect.

I find this incredibly interesting when comparing the two coaches, especially when considering the playbooks and players.

Mike Sherman had Brett Favre for his entire tenure, and McCarthy had Favre for two years and Aaron Rodgers the rest of the time. Also, Sherman had Ahman Green running behind a pretty dominant line using man-to-man blocking, and McCarthy has had several running backs and has used both zone and man-to-man blocking. Furthermore, McCarthy has received a lot of heat for not running the ball more, whereas Sherman once received a lot of praise for having a run-heavy offense with Green that took some pressure off of Favre as he got older.

Yet, almost no differences exist between the two coaches. If we look at the statistics alone, it does appear that play calling is overrated, or at least not influential in total scoring and yards achieved over multiple seasons.

So, is that the end of the story?

Of course not. Statistics can only explain so much. There must be more to the story. Player health, morale, psychology, luck, and weather all factor in somehow. Just look at how Sherman's team fell to the bottom in 2005 after absolutely dominating in 2004. There's a lot of psychology in precipitating that fall. Figuring out the statistics on all these factors can be someone's graduate thesis.

Also, I'm sure recent rule changes that favored the passing game factored into the significant differences in passing yards between Sherman and McCarthy.

As another point of comparison, Greg Easterbrook wrote in his Tuesday Morning Quarterback column back in 2009 that good coaching and play calling can improve a team by 10%. Any other improvements are the result of the talent on the field.

So, if we assume McCarthy is a better coach then Sherman, is there a 10% improvement?

These results are mostly the same as the t-tests and MANOVA and show that passing yardage increased under McCarthy. It also shows that McCarthy's offense had a 10% improvement in total yardage ranking (assuming a 10% improvement is a 3.2 ranking increase). 

I'm not sure how Easterbrook arbitrarily decided a good coach was worth 10%, but considering McCarthy was only better in 2 of 5 categories compared to Sherman, that's not a major vote of confidence to either Easterbrook's method or that McCarthy was better in general when only dissecting offensive numbers.

What Does This All Mean?

If you're still reading, we can interpret these results and make several conclusions:

1. Play calling does appear to be overrated when it comes to the Packers' offense. Sherman and McCarthy had similar numerical results with virtually no differences throughout their tenures except for a Super Bowl victory.
2. Play calling and statistics do not win Super Bowls. Apparently, something else is going on.
3. The Packers have had an unprecedented era of offensive brilliance. Between 2000-2014 (you could also throw in 1995-1998), they've had two play callers, two Hall of Fame quarterbacks, a herd of running backs, a flock of wide receivers, and a pretty unsettled tight end position lacking star power. Yet, they consistently ranked towards the top of the NFL's offenses. We have something special with the Favre and Rodgers eras.
4. From a statistical point, it appears that Sherman wasn't as bad as we imagined and McCarthy didn't have the level of improvement over Sherman that we may have thought.
5. This likely means that both Sherman and McCarthy were near equally good at coaching fundamentals and execution on the offensive side of the ball.
6. The play calling change entering the 2015 season probably won't mean much and it'll be more so the product of the talent on the field properly executing the plays. Expect similar results from previous years.