Does Quarterback Instability Derail an Offense?

I'll never forget the first time I watched the movie Bill & Ted’s Excellent Adventure, and my eyes were opened to a world of possibility in imagination. These two high school burnouts discovered that they would be responsible for creating world harmony in the future through their band (Wyld Stallyns!), but only if they passed their final history presentations.

In all honesty, that has to be the most ingenious and insidious way for adults to encourage teens to do their homework. Ever.

The story of Bill S. Preston, Esq. and Ted “Theodore” Logan didn’t just take us on a wild trip through time, though. It asked us to consider the future and our impact on the bigger picture. I started thinking about this while researching the effect that football teams changing their quarterbacks midway through a season had on the team’s offensive value. The Jets, the Bills, the Browns, the Buccaneers, and so many more teams before them have taken the “hot hand” approach and applied it to the most important position on the football field.

A head coach wants to give the team the best chance to win in any given week, so he’ll play who he thinks is best in the moment. It’s possible, however, that a lack of continuity under center ruffles a whole team, and possibly upsets a player’s own season. Perhaps, unlike the credits music from Excellent Adventure suggests, this is the one case where the phrase “Two heads are better than one” is not accurate. Let’s find out!

Iron Maiden? Excellent!

The theory behind this study is that, as an offense gets to know one signal-caller’s cadence, his hard counts, his way of moving in the pocket, all the little details of the way he plays, it becomes harder for them to adapt to a new quarterback stepping into the role. Simultaneously, as a quarterback gets more reps, he should get into a rhythm and comfort zone in the offense, without having to look over his shoulder in fear of a backup taking his job. Therefore, we want to see if teams that have a more even split in quarterback drop backs will have worse offensive production than those where one player leads the pack.

To figure this out, I grabbed our Net Expected Points (NEP) data for every quarterback who dropped back at least 100 times since 2000. After compiling this list, I looked for teams that had more than one quarterback dropping back at least 100 times in a season, and took only those passing units for this study. By tightening the search for our quarterback squads in this way, I tried to eliminate any possibility of a player suffering an injury that allowed an understudy to step in for a few games (Aaron Rodgers' 2013 season), rather than a true “by committee” approach (like Matt McGloin and Terrelle Pryor's 2013 Oakland Raiders).

With these sample subjects figured out, I then divided these units into two groups: those in very evenly-split situations (with no player taking over 65% of his team's total drop backs) and those with a greater split between the quarterbacks (one player at least 65% of the team drop backs). Does the hypothesis hold that greater instability under center causes team turmoil in the long run?

Be Excellent to Each Other

First, we'll look at how these units affect team play. The table below displays the average team NEP production and individual quarterback season for both nearly-even quarterback situations and passing units that favor one player. The goal here, again, is to discover if a greater amount of playing time a quarterback gets in his offense increases team offensive production. Does familiarity matter to the team effort?

Just as we expected, the teams with true committee situations (remember, this means no quarterback with more than 65% of his team's total drop backs) tend to have lower offensive output on average than those with more stability in their offenses. The difference is more than five touchdowns of offense per season overall, and four from the passing game alone. One can suggest that this might be self-referential, however -- that the reason teams with a greater disparity in snaps between their primary passer and backups have better scores is because those teams just have more talented quarterbacks. Perhaps this is true, but the committee approach teams also count among their number many great individual seasons by Kurt Warner, Michael Vick, Brian Griese, and so on.

There is a strong reason to believe that splitting time between your quarterbacks throws off the entirety of the offense, knotting it into a mess, when there might have been at least average production by sticking to one.

Party On, Dudes

What about specific player production, though? Does a lack of job security throw off a player himself? The next table shows us the difference in individual production between the lead quarterbacks in each of these two situations. We expect that, since a quarterback with more playing time was shown to offer more team production, that this situation should also lead to more personal production. Is that true in terms of Passing NEP?

In the immortal words of Bill and Ted: “Whoa.” It's not even close. We can reasonably expect that a player with a greater volume of drop backs will likely have a higher raw Passing NEP, due to more volume, but even in per drop back Passing NEP (which measures efficiency), these quarterbacks with more continuity have a higher score. This seems to confirm the idea that allowing a quarterback into a rhythm and a team to understand the quarterback more not only benefits the greater good, it also benefits the individual player.

Just for kicks, I also examined if there were any major outliers in the data. For instance, did any true committee situations occur on a majorly successful offense? I took every offensive season by Team NEP and Team Passing NEP since 2000 and figured out the benchmark to be in the top 10% of an offensive season in the past 15 years. For Team NEP this was 122.10, and for Team Passing NEP this threshold was 108.45. The only teams to cross both of these thresholds and still have no passer with more than 65% of his team's drop backs are shown below.

It's not a huge shock to see Warner represented with the "Greatest Show on Turf" Rams in this list, along with his counterpart Trent Green. However, Alex Smith is here as well, is a season where his efficiency was outstanding, and his backup Colin Kaepernick brought a massive amount of big-play explosiveness to the table for their 49ers. Oddly enough, Smith also accounts for the only other 90th percentile Team NEP season by a true committee, in 2005 with Tim Rattay as his other half, though their Team Passing NEP struggled massively.

What Have We Learned?

For a team or coach’s purpose, we’ve seen the data suggest that swapping quarterbacks like you’re putting gum on the antenna of your time-traveling phone booth will not get you anywhere. There’s a large benefit to team production suggested by having a consistent presence under center in your team's offense. For the individual player, too, efficiency skyrockets with added work and consistency of playing time. One has to think that if it’s good for the player, it’s probably good for the team too. If a player produces more efficiently the more he plays, I’d probably prefer to stick with the comfortable hand, not the “hot” one.

It may seem obvious, but sometimes we need to be reminded of the obvious and to not overthink it; after all, that strategy certainly worked for Bill and Ted.