Raise your hand if you have heard this recently: starting pitchers aren’t pitching as many innings as they once did. If your hand isn’t raised, you’re probably lying.

Is is true that starting pitchers aren’t the workhorses they once were. Since 2015, the amount of innings thrown by starting pitchers has constantly decreased, which has led to several complaints from spectators. It is very common to hear former players lament about how pitchers are used, with a consistent connection made towards working the third time through the order. After the Rays pulled Blake Snell in the sixth inning of Game 6 of the World Series while throwing a shutout, these grievances have only become louder.

The old-school thinking is that pitchers need to be pushed a third time through the order, and that a great amount of value of starting pitchers come from their ability to accumulate innings. On the other side of the spectrum, organizations like the Rays and Brewers are leading a new movement in which the bullpen takes a greater load of the innings share, while their starting pitchers are limited to around 120 innings a season.

With this being a two-sided debate, is there a clear right or wrong approach? Does old-school thinking still prevail, or has the game passed it by? To answer this, we will be analyzing data from 2015 to 2019, with 2020 being excluded due to it being a short season. With this study, the hope is that we can come to a conclusion as to where the value of starting pitchers stem from, and how teams should go about utilizing their pitches to maximize their run prevention efforts.

How Important Is It For Starting Pitchers To Eat Innings?

Are the best pitching staffs seeing their innings pitched totals dominated from starting pitchers or relievers? The answer is certainly with the former:

From this, we can imply that the more innings that can come from starting pitchers, the better. Intuitively, this makes sense. Teams are going to utilize the best pitchers, so the worse a team’s starting pitching is, the less innings they will accumulate, and the worse the team is likely to be in run prevention. Thus, I don’t see these results as “having relievers pitchers more is bad” as much as a self-selection bias.

Backing up that claim is how pitching usage has evolved over the past two years:

The correlation between innings from starting pitching and having a low ERA has decreased, while the inverse relationship between reliever innings pitched and ERA has lessened as well. In other words, getting innings from starting pitchers appears to be losing its value. The above scatterplot, however, shows how there isn’t a specific way that teams have to utilize their pitchers. Two of the fewest innings shares from starting pitchers led to a low ERA, and the same is true from some of the high innings shares. We often are looking for a binary answer, but, in reality, it appears that teams need to simply adjust their strategy to their organizational strengths and their personnel.

Are Starting Pitchers Still Valuable?

With starting pitchers being asked to pitch fewer innings, are they losing value? This is a critical question to answer. If the answer is “yes”, then we may need to question whether or not starting pitchers should still be getting the massive contracts they have been earning in free agency, while an emphasis may need to be placed on reliever depth. In the end, though, starting pitchers are as important as ever:

Obviously, it is important to have both quality starting pitchers and quality relievers, but it appears to be easier to survive having a poor bullpen rather than a struggling rotation. The Nationals, for instance, had one of the league’s worst-performing bullpens in 2019, but they still were able to be excellent in run prevention due to an excellent starting rotation. At the same time, the Padres and Red Sox ranked in the top-ten in relief pitcher WAR, yet also were in the bottom-half in terms of run prevention.

Over the past two seasons, these correlations are practically identical. Thus, even as teams continue to rely on their starting pitchers less, their value has not decreased. For this reason, team-building practices do not have to be altered in terms of how much to prioritize adding starting pitching. Having a strong rotation remains much more important than possessing a stout bullpen, and that is without mentioning the volatility of relievers. The Rockies, for instance, prioritized upgrading their bullpen over their rotation in the 2017 offseason, and the results have not panned out. At the same time, the Padres could have tried to build an elite bullpen this offseason, but, instead, they have focused on acquiring starting pitchers.

In fact, could you guess who committed the most amount of their payroll to relief pitchers in 2019? That would be the Marlins, who finished just outside the bottom ten in team ERA. Additionally, the Rockies (third-most resources, second-highest ERA) and White Sox (fifth-most resources, ninth-highest ERA) probably wish they would have allocated their resources better. Looking ahead to 2021, the Mets (most resources to relievers), Blue Jays (fifth-most), and White Sox (sixth-most) either should be looking to add more depth to their rotation, or have to hope that their investments in the rotation are sufficient enough. On the other side of the spectrum, the Reds may only have 2.42% of their payroll committed to relievers, but with Luis Castillo and Sonny Gray leading the charge, they should be fine. That is, if they avoid a complete stars and scrubs approach to constructing the rest of their starting rotation.

Efficiency or Volume?

So far, we have settled:

• Starting pitchers are being asked to pitch less innings
• They are still as valuable as ever

How could this be the case, you may ask? It all goes down to maximizing their efficiency, which has always been far more significant than their ability to eat innings:

Remember the idea that teams should pitch the pitcher best equipped to get the opposing batter out? That applies here. Yes, being able to accumulate innings pitched is important. What really matters, however, is the ability to prevent runs from being scored. If that can only happen over five-inning stints, so be it. There isn’t much value, though, in pitching extra innings that are inefficient. The idea of “innings eaters” is that they take the pressure off of a bullpen, but if you’re allowing extra runs, what is that accomplishing. I’d much rather take my chances with my bullpen that forcing a tired pitcher to work longer into a game.

Let us go back to Snell. Now on the Padres, many are excited about the idea that he may pitch longer into games than he did with the Rays. However, that frame of thinking is flawed. You cannot just extrapolate his run-prevention efficiency over a longer body of work. This isn’t about him allowing one run over five innings or one run over seven innings; if those were the options, Tampa would have him pitch longer. Rather, the Rays had to decide between him pitching less innings and allowing fewer runs, or him pitching more, less effective innings. With the amount of pitching depth they have, they chose the former option, which, in my opinion, appears to certainly be the rest decision.

At the end of the day, it is not about getting innings from your starting pitchers as much as possible, but, rather, to get as much value as you can. That means tailoring your pitching plan to your personnel. The Rays have the organizational depth to not force their starting pitchers to work deep into games, nor do they have the resources to acquire pitchers who can pitch deep into games and not lose their efficiency. The Nationals, on the other hand, have invested heavily on their rotation, so they have the personnel in place to allow them to pitch deeper into games. Ultimately, this is a case-by-case basis.

Overview

We often want a binary “yes or no” answer to every problem, but that often leads to unnecessary rigidity.

Old-school thinking that starting pitchers HAVE to work a third time through the order is certainly flawed, and the idea that pitchers are being constrained makes even less sense. Teams would love to have starting pitchers who can be efficient pitching deep into games, but there are only a select few who can do just that.

With that in mind, there is a lot of value in maximizing the efficiency of starting pitchers, which means asking them to not pitch as deep into games, assuming there are less effective when doing so. After all, the main goal is to get as much value from your starting pitchers as possible, and with efficiency mattering far more than volume, teams aren’t constraining pitchers as much as helping them be the best versions of themselves; their WAR totals are roughly the same as they were at the start of the decade.

Thus, teams need to be focused on accumulating as much pitching depth as possible. With that being the case, they can have their innings pitched by several pitchers, rather than those innings being concentrated to a select few. This is precisely why teams like the Rays and Brewers don’t need their pitchers to go deep into games; they have more than enough pitchers to be worried about getting innings from one specific pitcher.

Additionally, I wouldn’t be surprised if the idea of “piggybacking” pitchers becomes more common. For those unaware of this theory, it relates to two pitchers serving as “bulk options”- pitching around three innings each. This isn’t sustainable for a whole rotation, but can work as options as the #4 or #5 starter spots. The Astros used this often in the 2020 postseason, while the Brewers, Padres, and Rays have all utilized this approach to various degrees as well.

At the end of the day, smart organizations know that you need more than five starting pitchers and eight relief pitchers to get through a season, and honestly, there doesn’t need to be a distinction between “starter and reliever”. Rather, teams need to get 27 outs, and they need to do whatever it takes to allow the fewest amount of runs possible while getting those outs. The more teams focus on getting pitchers who thrive with run prevention, rather than simply eating innings, the more efficient they can continue to be constructing the best pitching staff imaginable. As for the value of a workhorse ace, they, as well as all starting pitchers, will continue to be an incredibly valuable part of the game, even as it continues to evolve.