The 2018 Brewers pitching staff out-played their expected Deserve Run Average performance by approximately 16 runs. On the whole, this is not quite that bad, as RHP Chase Anderson stands as an obvious outlier; Anderson outplayed his expected DRA performance by approximately 24 runs, which explains much of the difference between team DRA Runs Prevented and Average Runs Prevented.

**What’s Runs Prevented? **Flexible Elite Roles || Exploring Runs Prevented || Aces Do Not Exist || Rotation Spots || Third-Time Charmers

Here’s how the Brewers pitching staff looks when ranked by Average Runs Prevented. For additional context, each pitcher’s Games, Games Started, and Innings Pitched statistics are included.

*Stats: *

*Average Runs Prevented is the average of park-adjusted, league-adjusted estimates of a pitcher’s actual runs allowed compared to their expected runs allowed.*

*DRA Runs Prevented is the difference between a pitcher’s expected runs allowed and their DRA performance. *

*Direction* *is the “Direction of Change” between a pitcher’s 2018 Average Runs Prevented and 2018 DRA Runs Prevented.*

*G is “Games” (total appearances); GS is “Games Started” (total starts); IP is “Innings Pitched.”*

2018 Brewers | Average Runs Prevented | DRA Runs Prevented | Direction | G | GS | IP |
---|---|---|---|---|---|---|

Jeremy Jeffress | 24.6 | 15.1 | -9.5 | 73 | 0 | 76.7 |

Josh Hader | 15.8 | 21.6 | 5.9 | 55 | 0 | 81.3 |

Wade Miley | 10.5 | 2.4 | -8.1 | 16 | 16 | 80.7 |

Jhoulys Chacin | 9.0 | -2.5 | -11.5 | 35 | 35 | 192.7 |

Corbin Burnes | 7.1 | 4.2 | -2.8 | 30 | 0 | 38.0 |

Gio Gonzalez | 5.0 | 3.2 | -1.8 | 5 | 5 | 25.3 |

Chase Anderson | 4.3 | -19.8 | -24.1 | 30 | 30 | 158.0 |

Dan Jennings | 3.8 | -3.8 | -7.6 | 72 | 1 | 64.3 |

Corey Knebel | 3.4 | 11.5 | 8.1 | 57 | 0 | 55.3 |

Jorge Lopez | 3.3 | 1.2 | -2.1 | 10 | 0 | 19.7 |

Xavier Cedeno | 2.8 | 1.1 | -1.7 | 15 | 0 | 8.0 |

Brandon Woodruff | 2.4 | 5.8 | 3.4 | 19 | 4 | 42.3 |

Adrian Houser | 1.5 | -1.0 | -2.5 | 7 | 0 | 13.7 |

Alec Asher | 1.5 | -0.3 | -1.8 | 2 | 0 | 3.0 |

Jordan Lyles | 0.8 | 3.3 | 2.5 | 11 | 0 | 16.3 |

Freddy Peralta | 0.5 | -7.1 | -7.6 | 16 | 14 | 78.3 |

Joakim Soria | -0.5 | 3.6 | 4.0 | 26 | 0 | 22.0 |

Erik Kratz | -0.6 | -0.5 | 0.0 | 3 | 0 | 3.0 |

Jacob Barnes | -0.8 | 4.6 | 5.4 | 49 | 0 | 48.7 |

Boone Logan | -1.8 | -1.8 | 0.0 | 16 | 0 | 10.7 |

J.J. Hoover | -2.4 | -0.5 | 1.8 | 2 | 0 | 1.3 |

Taylor Williams | -2.7 | 0.3 | 3.0 | 56 | 0 | 53.0 |

Oliver Drake | -3.0 | 2.6 | 5.6 | 11 | 0 | 12.7 |

Hernan Perez | -3.4 | -1.8 | 1.7 | 3 | 0 | 3.3 |

Zach Davies | -4.7 | -2.1 | 2.6 | 13 | 13 | 66.0 |

Aaron Wilkerson | -5.7 | -1.6 | 4.1 | 3 | 1 | 9.0 |

Mike Zagurski | -6.5 | -0.1 | 6.4 | 2 | 0 | 1.0 |

Brent Suter | -6.6 | -6.9 | -0.3 | 20 | 18 | 101.3 |

Junior Guerra | -6.7 | -1.7 | 5.0 | 31 | 26 | 141.0 |

Matt Albers | -12.6 | -6.5 | 6.1 | 34 | 0 | 34.3 |

Why is this important? DRA is a pitching statistic that estimates each pitcher’s performance based on numerous contextual factors. DRA is a statistic that can describe a player’s performance on the field by correlating Runs Allowed per 9 IP (RA9) to DRA; it is modeled to consistently assess a player’s performance year-to-year; and it is modeled to predict next year’s RA9. Runs Prevented, on the other hand, is a purely descriptive statistic, simply aiming to measure the extent to which a pitcher compares to their park and league environments.

Before we get into the extended analysis, if you’d like to know why this topic is important, consider the following questions; for fun, the exercise could also end here, as there’s a lot to think about with this staff.

….which of these pitchers would you expect to improve in 2019?

2018 Brewers | Average Runs Prevented | DRA Runs Prevented | Direction | G | GS | IP |
---|---|---|---|---|---|---|

Jordan Lyles | 0.8 | 3.3 | 2.5 | 11 | 0 | 16.3 |

Zach Davies | -4.7 | -2.1 | 2.6 | 13 | 13 | 66.0 |

Taylor Williams | -2.7 | 0.3 | 3.0 | 56 | 0 | 53.0 |

Brandon Woodruff | 2.4 | 5.8 | 3.4 | 19 | 4 | 42.3 |

Joakim Soria | -0.5 | 3.6 | 4.0 | 26 | 0 | 22.0 |

Aaron Wilkerson | -5.7 | -1.6 | 4.1 | 3 | 1 | 9.0 |

Junior Guerra | -6.7 | -1.7 | 5.0 | 31 | 26 | 141.0 |

Jacob Barnes | -0.8 | 4.6 | 5.4 | 49 | 0 | 48.7 |

Oliver Drake | -3.0 | 2.6 | 5.6 | 11 | 0 | 12.7 |

Josh Hader | 15.8 | 21.6 | 5.9 | 55 | 0 | 81.3 |

Matt Albers | -12.6 | -6.5 | 6.1 | 34 | 0 | 34.3 |

Mike Zagurski | -6.5 | -0.1 | 6.4 | 2 | 0 | 1.0 |

Corey Knebel | 3.4 | 11.5 | 8.1 | 57 | 0 | 55.3 |

….which of these pitchers would you expect to improve in 2019?

2018 Brewers | Average Runs Prevented | DRA Runs Prevented | Direction | G | GS | IP |
---|---|---|---|---|---|---|

Gio Gonzalez | 5.0 | 3.2 | -1.8 | 5 | 5 | 25.3 |

Alec Asher | 1.5 | -0.3 | -1.8 | 2 | 0 | 3.0 |

Xavier Cedeno | 2.8 | 1.1 | -1.7 | 15 | 0 | 8.0 |

Brent Suter | -6.6 | -6.9 | -0.3 | 20 | 18 | 101.3 |

Boone Logan | -1.8 | -1.8 | 0.0 | 16 | 0 | 10.7 |

Erik Kratz | -0.6 | -0.5 | 0.0 | 3 | 0 | 3.0 |

Hernan Perez | -3.4 | -1.8 | 1.7 | 3 | 0 | 3.3 |

J.J. Hoover | -2.4 | -0.5 | 1.8 | 2 | 0 | 1.3 |

….which of these pitchers would you expect to improve in 2019?

2018 Brewers | Average Runs Prevented | DRA Runs Prevented | Direction | G | GS | IP |
---|---|---|---|---|---|---|

Chase Anderson | 4.3 | -19.8 | -24.1 | 30 | 30 | 158.0 |

Jhoulys Chacin | 9.0 | -2.5 | -11.5 | 35 | 35 | 192.7 |

Jeremy Jeffress | 24.6 | 15.1 | -9.5 | 73 | 0 | 76.7 |

Wade Miley | 10.5 | 2.4 | -8.1 | 16 | 16 | 80.7 |

Dan Jennings | 3.8 | -3.8 | -7.6 | 72 | 1 | 64.3 |

Freddy Peralta | 0.5 | -7.1 | -7.6 | 16 | 14 | 78.3 |

Corbin Burnes | 7.1 | 4.2 | -2.8 | 30 | 0 | 38.0 |

Adrian Houser | 1.5 | -1.0 | -2.5 | 7 | 0 | 13.7 |

Jorge Lopez | 3.3 | 1.2 | -2.1 | 10 | 0 | 19.7 |

By describing Runs Prevented and DRA Runs Prevented statistics year-over-year, it is possible to understand the absolute volatility of pitching performance. DRA is also potentially a tool that can be used to set someone in the right direction for analyzing statistical profiles in order to project improvement or decline.

Let’s take a look at MLB pitchers that worked in 2017 and 2018:

2017 to 2018 Pitchers | Absolute Value of Change |
---|---|

Runs Prevented | 9 |

Innings Pitched | 33 to 34 |

Games Started | 4 |

2018 SP Runs Prevented | 11 to 12 |

2018 SP Innings Pitched | 49 to 50 |

2018 SP Games Started | 9 |

2017 SP Runs Prevented | 12 |

2017 SP Innings Pitched | 48 to 49 |

2017 SP Games Started | 9 |

Count: 639 MLB Pitchers |

The value of using a statistic such as DRA is that the year-to-year Runs Prevented performance by MLB pitchers is absurdly volatile. The table above demonstrates the absolute value of change in several key statistics for pitchers that worked in both 2017 and 2018. 639 MLB pitchers worked in both 2017 and 2018 seasons. On the whole, this group was quite volatile, with the *average* change in runs prevented moving by nine runs prevented (positive or negative); a pitcher that worked in both 2017 and 2018 also saw their innings pitched total fluctuate between 33 and 34 innings, and their average games started fluctuate by four. Focusing specifically on starters (i.e., pitchers who started a game in 2017 and pitchers who started a game in 2018), the fluctuations are even wider.

These fluctuations would be the equivalent of Jhoulys Chacin becoming a slightly below average, slightly smaller workload pitcher in 2018, or improving steadily into “ace” territory; Freddy Peralta expanding into a more regular rotation role, or stepping back into a smaller replacement role; Corey Knebel fluctuating to a below average reliever or recovering his excellent high leverage form; or Josh Hader becoming “just” an average reliever or taking the next step in his high leverage ace development. These are just a few examples of the real impact that typical run prevention fluctuations can cause to a team. Each of these pitchers are likely to remain under Brewers contractual control in 2019, so it *matters* how their performances change.

Let’s dig deeper into that group of 639 pitchers that worked in both 2017 and 2018 to assess the descriptive value of DRA and Runs Prevented. A couple of caveats are in order. First, this is a biased analysis, insofar as I am expressly limiting my search to players that worked in both 2017 and 2018, which excludes a “true talent assessment” of players that missed either of those seasons for a multitude of reasons (from player development, such as Freddy Peralta, to injury, such as Jimmy Nelson). Second, since I will be describing the general direction of DRA, I am not using statistical methods to assess the significance of DRA’s predictions. With these caveats in mind, I think it remains useful to see how DRA assesses players within a single season, and across two seasons.

Runs Prevented (RnsPrv) | Pitchers |
---|---|

Improve | 254 |

Decline | 296 |

Minimal Change (-2 < RnsPrv < 2) | 89 |

Now that we’ve discussed the average absolute value of Runs Prevented change between 2017 and 2018, let’s take an overview of this group of pitchers in terms of improvement or decline. Excluding pitchers with Runs Prevented totals between -2 and 2 in 2017 *and* 2018, which represents a relatively minimal range of fluctuation that could simply be explained by park factors or league environment, more pitchers declined than improved between 2017 and 2018. In many cases, these changes were quite major, as 132 pitchers declined by 10 or more Runs Prevented, while 53 pitchers improved by 10 or more Runs Prevented. The overall magnitude of major declining performances ensured that this group of 639 pitchers was -439 Runs Prevented (!!!) between 2017 or 2018; this means that if each 2017 team retained these pitchers, on average they would have been expected to lose approximately 44 more games (as a group) in 2018, all else held equal.

Based on 2017 performance, could anyone have predicted these directions of change among these pitchers? Once I assembled an Average Runs Prevented analysis of the 2017 MLB season, and isolated pitchers that worked in both 2017 and 2018, I analyzed several aspects of each player’s performance:

- I analyzed the 2017 Direction of Change, which is the change between 2017 Runs Prevented and 2017 DRA Runs Prevented, in order to assess whether a player overperformed or underperformed their DRA.

- I analyzed the 2017 Direction of Change and the difference between 2018 Runs Prevented and 2017 Runs Prevented, in order to assess whether a player’s between-seasons change (2017 to 2018) matched their 2017 underperformance or overperformance. Focusing on 2017 Direction of Change and between-seasons change is one way to describe the types of projections made by DRA.

- I assessed 2017 DRA Runs Prevented and 2018 DRA Runs Prevented in order to determine whether the statistic consistently estimated a pitcher’s contextual performance.

First and foremost, in terms of 2017 and 2018 consistency, DRA consistently assessed 389 pitchers as either Above Average or Below Average in both 2017 and 2018. Since the “Other Pitchers” group is quite a set of outliers, I provided a couple of key statistics about their DRA Runs Prevented.

DRA 2017 & 2018 | Statistic |
---|---|

Below Average Pitchers | 207 Pitchers |

Above Average Pitchers | 182 Pitchers |

Other Pitchers | 250 Pitchers |

Other: Absolute Value of DRA Change | 10.4 DRA Runs Prevented |

Other: Minimal DRA Change (<4 R) | 66 Pitchers |

Other: Major DRA Change >20 R) | 33 Pitchers |

In this case, the “Other” group is comprised of outliers, including pitchers like Wade Miley and Chase Anderson, as well as Lucas Giolito, Kyle Freeland, and Derek Holland, among others. This is an area where the biased selection of this group of pitchers could impact analysis, as developments such as a new pitch (by Miley) or backed-up stuff and command (by Giolito) create role discrepancies that would be difficult to predict without granular scouting information. Of course, these are precisely the types of uneven player development facts that teams attempt to exploit. Wade Miley *was* not a particularly good pitcher in 2018, indeed he could have reasonably been replaced (which is partially why he was available for a minor league contract entering 2018); his development to an average pitcher was worth 44 DRA Runs Prevented between 2017 and 2018, a massive improvement that is going to skew nearly any sample of players.

On the whole, it is worth noting that DRA Runs Prevented tracked *better* than Average Runs Prevented, in terms of absolute value of change, between 2017 and 2018. Among pitchers that worked in both seasons, DRA Runs Prevented fluctuated by approximately 8 runs, compared to approximately 9 runs by Average Runs Prevented. Not bad!

How does DRA work with this group of pitchers in terms of predicting the general direction of change between 2017 and 2018? Based on a pitcher’s internal 2017 difference between DRA and Runs Prevented, that pitcher’s typical improvement or decline between 2017 or 2018 matched the overperformance or underperformance (in terms of 2017 DRA versus 2017 Runs Prevented). DRA correctly assessed a pitcher’s expected performance change in 79 percent of cases:

2017 Direction of DRA vs. Actual Runs Prevented | Number of Pitchers |
---|---|

Predicted Improvement | 227 |

Predicted Decline | 275 |

Other Prediction | 137 |

Within this group of pitchers, DRA performs quite well in terms of assessing the actual size of the Runs Prevented change, as well as the direction. Once I categorized pitchers into groups of players that had Predicted Improvement, Predicted Decline, or some Other Prediction, I compared the change between 2017 and 2018 DRA Runs Prevented to 2017 and 2018 Actual Runs Prevented:

DRA Prediction and Direction of Change | Average DRA Prediction | Average Actual Direction | Total DRA Prediction Runs | Total Actual Direction Runs | Absolute Value DRA Prediction Runs | Absolute Value Actual Runs | Absolute Value % |
---|---|---|---|---|---|---|---|

Predicted Improvement | 9.9 | 9.7 | 2238 | 2213 | 2501 | 2213 | 88% |

Predicted Decline | -12.8 | -10.5 | -3507 | -2884 | 3578 | 2884 | 81% |

Other | -0.6 | 1.3 | -78 | 178 | 991 | 781 | 79% |

It should be underscored that this is a *descriptive* account of DRA’s predictions, rather that a statistical test of the significance of DRA’s predictions. Still, what is incredibly impressive about DRA is just how strong the statistic is in anticipating the *shape* of the run environment, and understanding the wide variance that can occur year over year.

What is interesting is that, according to DRA, the Brewers pitching staff was indeed better than average in 2018. However, there are 22 pitchers from that staff that might reasonably be expected to post a notable improvement or decline in 2019, if one assesses the extent to which they outperformed or underperformed their 2018 DRA. Thus, it is worth repeating the questions about who might be expected to improve in 2019, for even if the overall direction of the club’s pitchers may be expected to stay the course, their shape and distribution of Runs Prevented can all but expected to look quite different.