Who will pitch in the bullpen?
The answer to that question changed after my third draft of this article.
- Part one is my first snapshot of opening day bullpen pitchers from FanGraphs.
- Part two is my latest prediction of the opening day bullpen pitchers, which is mostly the same as FanGraphs, but with differences.
PART ONE – FIRST SNAPSHOT.
Per FanGraph’s Roster Resource, a snapshot of the opening day bullpen included:
- Ryan Thompson
- Andrew Saalfrank
- Kevin Ginkel
- Brandyn Garcia
- Andrew Hoffman
- Drey Jameson
- Taylor Clarke
- Jonathan Loáisiga
Let’s focus on those eight pitchers.
Two team-specific ways to look at bullpen results.
At a top level, each pitcher’s team specific results from last season will provide insight into this season.
For the pitchers expected to be in the bullpen, two basic statistics are:
- limiting homers.
- maximizing strikeouts per walk.
Data was obtained from Stathead and Baseball Reference.
As a starting point, let’s look at their 2025 pitching against the top three
teams for homers and top three teams for minimizing strikeouts per walk. For each statistic, each pitchers’ results against the other teams were excluded.
Homers per PA. The best batters played for the Yankees, Dodgers, and Mariners. These three teams know best how to hit homers. The three-team average was .041 homers per PA.
When the eight Diamondbacks’ bullpen pitchers pitched against those three teams, their combined homers per PA was .054. My conclusion is that the bullpen was worse than average in preventing homers, when homers were a strength of the other team.
(Strike Outs minus Walks) per PA. The best batters played for the Blue Jays, Padres, and Royals. These three teams know best how to minimize strikeouts compared to walks. The three-team average was .103 (K-BB)/PA.
When the eight Diamondbacks’ bullpen pitchers pitched against those teams, their combined (K-BB)/PA was .045. My conclusion is that the bullpen was very much worse than average in maximizing strikeouts compared to walks, when doing the opposite was a strength of the other team.
So far, the 2025 results of anticipated bullpen pitchers are not encouraging. But the Diamondbacks don’t often play the best teams (except in the playoffs). In general, most games will be pitched against teams in the NL West. The next step is to compare the bullpen pitchers’ results against other teams in the NL West.
Will the bullpen limit homers against teams in the NL West?
In general, most games will be pitched against teams in the NL West. The next step is to compare the bullpen pitchers’ homers allowed against other teams in the NL West.
Homers per PA. In the NL West (excluding the Diamondbacks) the four-team average was batting .030 homers per PA. When the eight Diamondbacks’ bullpen pitchers pitched against those four teams, their combined homers per PA was .030. In the NL West, the eight bullpen pitchers were average.
Homers per PA, if Dodgers are excluded. It is arguable that the Dodgers are a home run powerhouse, and therefore NL West results against non-Dodgers teams could be more impactful. The next step is to compare the bullpen pitchers’ homers allowed against the other three teams in the NL West, (excluded the Dodgers).
In the NL West (excluding the Diamondbacks and Dodgers) the three-team average was batting .027 homers per PA. When the eight Diamondbacks’ bullpen pitchers pitched against the remaining three teams, their combined homers per PA was .019. In the NL West excluding the Dodgers, the eight bullpen pitchers were very much better than average.
Will the bullpen limit (K-BB)/PA against teams in the NL West?
In the NL West (excluding the Diamondbacks) the four-team average was .14 (K-BB)/PA. When the eight Diamondbacks’ bullpen pitchers pitched against those four teams, their combined (K-BB)/PA was .09. In the NL West, the eight bullpen pitchers were worse than average in maximizing strikeouts compared to walks.
PART TWO – LATEST PREDICTION.
My view of who will be the opening day bullpen pitchers follows.
- Ryan Thompson
- Kevin Ginkel
- Brandyn Garcia
- Taylor Clarke
- Jonathan Loáisiga
- Kade Strowd
- Paul Sewald
- Michael Soroka
The biggest assumptions are that Jameson gets optioned to AAA, Loáisiga makes the opening day roster, and Soroka gets pushed from the rotation to the bullpen. The assumptions are reasonable, but by no means certain. Let’s focus on these eight pitchers. The big question is whether they would outperform the first snapshot despite the loss of Saalfrank.
The following table compares the first snapshot pitchers to my latest predicted pitchers. The remarkable improvement is in strikeouts minus balls [(K-BB)/PA]. Circled in green is the NL West stat, which shows that the latest bullpen moves made a significant predicted impact. Data from Stathead, Baseball Reference.
To answer our overall question, unlike the earlier bullpen snapshot, my latest predicted pitchers will make a significant positive impact in games against teams in the NL West.
Summary.
PART ONE. Based on a preliminary first snapshot of who will be the opening day bullpen pitchers, looking at limiting homers and maximizing strikeouts minus walks, two conclusions were:
- The eight bullpen pitchers as a group were worse than average in preventing homers, when homers were a strength of the other team.
- The eight bullpen pitchers as a group were worse than average in maximizing strikeouts compared to walks, when doing the opposite was a strength of the other team.
Looking at the bullpen pitching in the NL West, conclusions were:
- The eight bullpen pitchers as a group were average in preventing homers.
- Excluding the Dodgers, the eight bullpen pitchers as a group were very much better than average in preventing homers.
- The eight bullpen pitchers as a group were worse than average in maximizing strikeouts compared to walks.
PART TWO. Several changes happened; Saalfrank was injured, Sewald & Stowd were acquired, and Gallen was acquired. Based my latest prediction of who will be pitching in the bullpen, the changes in who will pitch in the bullpen made a significant positive impact on predicted strikeouts minus walks, especially for the NL West.
