Effectiveness of Modern Bullpens

Long gone are the days of a lefty striding confidently in from the bullpen with one goal and one goal only: to get the next man out. MLB implemented its 3-batter rule change (effective with the start of the 2020 season, and now most assuredly permanent) to make the game move faster and ensure more runs are scored. The verdict is still out on the effects.

Regardless though, these changes have forced an even greater analytical approach by coaching staffs to ensure more versatile pitching and proper implementation of player rotations. To create bullpens that are built for modern day baseball means pushing the limits of many pitchers’ abilities and returning to the fundamentals for success. So how does a team build a top tier bullpen? What should we be looking for?

To begin, let’s not ignore the fact that with relief pitching you typically get what you pay for. And even teams that are loaded with arms are not typically developing their top prospects for a life in the bullpen. While you will have certain pitchers at the minor league levels getting primed for a future as a reliever, most of these players are going to be starters sooner rather than later if they have the potential to dominate major league hitters. So, we’re often working with unknown quantities when it comes to analyzing bullpen pitchers.

At the end of the day the management of their bullpen is arguably the most important aspect in terms of a team’s overall “health” and potential for success. So monitoring bullpens certainly matters, especially late in the season when arms tend to get worn down and starters tend to inevitably struggle or end up on the injured list. These unexpected moments are the basis of the stress that taxes bullpens but also create a potential edge for those recognizing in advance a team is not prepared to perform at peak levels.

Indicators and Meaningful Stats

Questions often begin along the lines of how can relief pitching analytics really matter? Aren’t the sample sizes just too small for most relievers? How does looking at season long numbers help me today? What am I going to do with this information?

Regardless of whether you are simply a die-hard sports fan, are an analytics nut (like us), visit the sportsbook on occasion, play daily fantasy sports, or play season long fantasy baseball; there are some key considerations that can help bolster your understanding of the potential for a bullpen rotation. By combining a few fundamentals of baseball analytics, a complete analysis of current conditions, and a little critical thinking we have the ability to create a snapshot predicting a bullpen’s ability (with reasonable certainty) on any given day.

Plenty will voice their opinions on what matters most. From xFIP, to zone contact percentage, to SIERA and even those who archaically claim that ERA is still the most important, bottom-line metric. If you have an opinion, that’s great, the process that has led to you to successful analysis does not have to change, but there are a set of data points and calculations we’ve put together here, specifically with bullpen pitching in mind, that you simply cannot find anywhere else.

So, what factors do matter when analyzing a bullpen as a unit?

Overall Effectiveness

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