Let’s be prepared to compare a relief pitcher acquisition to bullpen candidates.
In the next few months, the Diamondbacks are likely to acquire a relief pitcher, probably via trade or waiver claim. And it is possible that Jordan Montgomery or Ryne Nelson start the season pitching long relief. Let’s look at how we can compare a new pitcher acquisition to the existing relief pitchers.
Statistics to compare relief pitchers.
My view is that saves and ERAs are poor statistics to compare relief pitchers. There are five statistics that can more meaningfully compare relief pitchers. They are Got-The-Job-Done (GTJD) (no earned runs and no inherited runners scored), percentage shutdown games (at least .06 Win Probability Added, WPA), percentage meltdown games (at least negative .06 WPA), strikeouts per batter faced (SO/BF), whiffs per pitch thrown.
One additional statistic for relievers with velocity over 94 MPH: when he finds a way to increase his velocity, it is reasonable to expect increased performance per this FanGraphs article. The caveat is that we have to wait until spring training to see whether any reliever improved his velocity.
In addition, looking at bWAR and fWAR can provide insights. While bWAR indicates past performance, fWAR can better indicate future performance potential (except for a few pitchers who manage contact well). For the purpose of comparison, when fWAR is significantly greater than bWAR it indicates that there is strong potential for that pitcher to improve in the following season.
Diamondbacks Relievers for next season.
Instead of looking at all Diamondbacks’ relievers from last season, let’s look at a group of pitchers that could reasonably start next season in the Diamondbacks’ bullpen (in the absence of any acquisitions).
The following table looks at the five statistics and my demarcation line for each metric. Key for table:
- Green means met or exceeded demarcation, black means close, and red means fell short.
- Shaded in yellow means they may not be ready to play until after opening day,
- Shaded in golden means they are not on the 40-man roster and were invited to spring training.
- Shaded in blue means they were a rotation pitcher last season who could possibly move to the bullpen.
Data from Baseball Reference and FanGraphs.
The following table shows the bWAR and fWAR for each pitcher (for 2024 unless otherwise noted). When fWAR is better than bWAR, it could indicate strong potential to improve next season.
Data from Baseball Reference and FanGraphs.
Discussion of the Relievers.
The following four pitchers are tier 1, the best in the Diamondbacks bullpen. Another way to say it is these are the A team.
AJ Puk. He met or exceeded the demarcation for all five of the statistics. He is the gold standard for the Diamondbacks bullpen.
Last season, he was the Diamondbacks’ best left-handed pitcher. That’s good. More than that, he was one of the best relief pitchers in the Majors! For details, see his player review.
Justin Martinez. He met or exceeded four of the five statistics. His four-seam fastball and his sinker had velocities greater than 100 MPH per Baseball Savant. He is clearly the second best pitcher in the bullpen. His fWAR was less than his bWAR, suggesting some regression next season. On the other hand, at 23 years old he is young and it’s possible that next season he will improve his pitching.
He started the season in low leverage situations and as the season progressed he entered the game in more high leverage situations. Perhaps his only weakness was too many walks. For details, see his player review.
Kevin Ginkel. He met or exceeded three of the five statistics. In addition he was close to meeting the shutdon statistic. His fWAR was better than his bWAR, pointing to a possible improvement next season.
Currently, he has the longest seniority in the Diamondbacks bullpen (2019 was his first season in the Diamondbacks bullpen).
His season had dominant stretches and bumpy stretches. He allowed only 14% of inherited runners to score (best of Diamondbacks). For details, see his player review.
Joe Mantiply. He met or exceeded two of the five statistics. His fWAR was better than his bWAR, pointing to a possible improvement next season.
In 2022, he was an All-Star. Last season he improved his ERA, BABIP, and especially his HR/FB. Although it did not seem to impact his performance, his velocity dropped by about a half MPH. For details, see his player review.
The following three pitchers are tier 2. They are good relievers.
Ryan Thompson. He met or exceeded two of the five statistics.
His bWAR reflects his high value to the Diamondbacks. On the other hand, his hard hit % rose from 34.1% to 44.6%. In the last two months of the season, he pitched two ‘clunker’ games. For details, see his player review.
Seth Martinez. He met or exceeded two of the five statistics.
In November, he was claimed on waivers. One reason to expect better results is better infield defense (positive 35 vs negative 4) This better defense will encourage him to return to how he pitched in April and May (higher ground ball % and pitch to contact instead of going for strikeouts). He is very similar to Joe Mantiply, who has thrived with the Diamondbacks. For details, see this AZ Snake Pit article.
Kyle Nelson. He met or exceeded two of the five statistics. In addition, he was close to meeting whiffs per pitch.
He may not be ready at the start of the season due to thoracic outlet surgery. Prior to sugery, he tried to gut it out, meaning last season’s performance may have been impacted by the condition. He is third on the depth chart of left-handed pitchers. For details, see his player review.
The following pitchers are tier 3. This tier includes the ‘others’ and long relievers. Perhaps their bullpen assignments will be temporary and intermittent.
Jeff Brigham. In 2023, his 26% strikeouts per batter faced was great.
In December, he signed a minors contract with an invite to spring training. He pitched in the Majors from 2018 to 2023. Last season, he pitched in AAA. He could provide experienced depth to the bullpen. For details, see this MLBTR article.
Drey Jameson. In 2023, he met or exceeded three of the five statistics.
Tommy John surgery caused him to miss last season. Whether he will be back on opening day is uncertain. For details see his player review.
Bryce Jarvis. He is the first of three possible long-relief pitchers. His fWAR is much worse than his bWAR, an indication that next season’s results could be worse. On August, a sprained elbow ended his season, but he may be back by opening day.
He pitched better late in the season. His fastball has above average velocity. For details, see his player review.
Ryne Nelson. He met or exceeded two of the five statistics. In addition, his GTJD was close to the demarcation line. His fWAR was better than his bWAR, pointing to a possible improvement next season.
He is another possible long-relief pitcher. My view is that two better options are include Ryne Nelson in a 6-man rotation, and keep Ryne Nelson in the minors until needed.
For discussion of his secondary pitches and details about his success in the rotation, see his player review.
Jordan Montgomery. He met or exceeded two of the five statistics. His fWAR is much better than his bWAR, an indication that next season’s results could be better.
A big reason to move him to the bullpen was his 6.40 ERA as a starter (21 games). With two games started as a minimum, only Tommy Henry had a worse ERA as a starter (6.47 ERA in 7 games). On the other hand, Montgomery’s 4.49 FIP as a starter indicates next season’s results could be better.
“The key question is probably the degree to which the team thinks Montgomery will bounce back.” — Jim McLennan, November 2024
A Bullpen Problem
This AZ Snake Pit article written by 1AZfan1 shares his view of the problem with the bullpen. His article states the root cause of last season’s bullpen failure was pitchers with less than 50 innings pitched (called the ‘others.’) They were “brutally bad.”
Let me point out that the ‘others’ included AJ Puk. My view is that Puk should have been included in the ‘stalwarts’ instead of the ‘others’ because he was acquired on 25 July, and as a Diamondback he pitched at a pace that would have reached 80 innings in a full season. With that one change, the ‘others’ were worse than brutally bad (words fail me).
The good news is that my table of pitchers who could possibly start next season in the bullpen only includes 3 of last season’s ‘others.’ They were Kyle Nelson and two rotation pitchers with less than 50 innings in the bullpen last season (Jordan Montgomery and Ryne Nelson).
Summary.
When the Diamondbacks acquire a new pitcher for the bullpen, five statistics can compare the new pitcher to existing candidates. They are:
- Got-The-Job-Done (GTJD) (no earned runs and no inherited runners scored).
- Percentage shutdown games (at least .06 WPA).
- Percentage meltdown games (at least negative .06 WPA).
- Strikeouts per batter faced (SO/BF).
- Whiffs per pitch thrown.
Another factor is whether the pitcher will improve. Two ways to look at it:
- Pitch velocity in spring training.
- fWAR compared to bWAR.
The bullpen candidate pitchers are in three tiers: the best (A team), the good relievers (B team), and the ‘others’ (which includes long relievers).
AJ Puk is the gold standard, meeting or exceeding the demarcation line for all five statistics. The rest of the top tier are Justin Martinez, Kevin Ginkel, and Joe Mantiply. The second tier pitchers are Ryan Thompson, Seth Martinez, and Kyle Nelson.
Three candidates for the long reliever in the bullpen are Bryce Jarvis, Ryne Nelson, and Jordan Montgomery.