Predicted Diamondbacks Bullpen - Way Too Early

The competition for roles in the Diamondback bullpen is wide open. Although spring training games will provide useful information, they have not yet started. Insider information would help, but I don’t have any. Experience working with pitchers would help, but I don’t have any. Deep baseball knowledge (think of Jack Sommers) would help, but I lack that depth.

Therefore, predicting who will have a bullpen role on opening day is challenging. I’ll be bold and take on that challenge.

Two assumptions.

First assumption: The starting 5 pitchers on opening day will not be considered for the bullpen. The assumed 5 starters are Madison Bumgarner, Zac Gallen, Merrill Kelly, Luke Weaver, and Caleb Smith. That assumption includes uncertainty. Injuries happen. And role changes are possible. For example on the AZ Snake Pit website, Jack Sommers explained why Luke Weaver should be converted to a short reliever or closer.

During the season, it is likely that the Diamondbacks will add four additional starting pitchers: Two will start the season in the bullpen and two will start the season in the minors.

Second assumption is an 8-man bullpen. That decision balances 13 pitchers with 13 position players. Prior to this article being posted, the Diamondbacks signed a pitcher that changed that assumption from an 8-man bullpen to a 9-man bullpen.

Four objective criteria.

Let’s look at objective criteria to compare the candidates for the bullpen.

Experience matters. An article indicated that Diamondbacks pitchers had an average of 350 innings in the minors before their debut in the Majors. It’s a leap, but my conclusion follows. Pitchers with significantly less than 350 innings pitched are not yet ready for the very competitive Diamondback bullpen.

Command of pitches matters. To compare all the candidates, I needed an objective measure that is available in the minors and Majors. My choice was the ratio of strikeouts to bases on balls (SO/BB). Because the team is counting on bouncing back to 2019 (instead of repeating 2020), let’s look at SO/BB for 2019. For players with 2019 innings in the minors and Majors, the innings weighted average of SO/BB will be compared.

Run prevention matters. To compare all the candidates, my choice was ERA. ERA was chosen for the same reasons as SO/BB, and the innings weighted averages for 2019 will be compared.

Second best pitch matters in the bullpen. I’ll introduce this idea with a caveat that there are always exceptions. Good relievers need a very good second pitch. Otherwise, batters will know to expect the best pitch and knowing it is coming they will often hit it effectively. My choice was to look at FanGraphs’ pitch values (runs above average per 100 pitches). Because the numbers change by a lot every year, the average for all seasons was chosen.

For 30 pitchers who were invited to spring training, I looked at those four factors (experience, SO/BB, ERA, and second best pitch). No one pitcher ranked highest in all four measures. Instead, six pitchers stood out as generally better, usually with one weakness.

That six pitchers turned into seven pitchers when the Diamondbacks signed Tyler Clippard (see AZ Snake Pit article by Jack Sommers). Tyler Clippard stood out in all four objective criteria.

Although Ryan Buchter’s SO/BB was lower than average, his other measures stood out. Although Humberto Castellanos had significantly less than 350 innings pitched, his SO/BB and ERA ranked very high. Although Chris Devenski, Riley Smith, and Joakim Soria had weaker ERAs than some pitchers, their other measures were excellent.

In my opinion, the top 7 candidates follow:

Data from Baseball Reference and FanGraphs.

Although 2020 results were not significant in selecting the seven candidates, what happened that season for these pitchers? Although small sample size applies, four had great results and three had lesser results. The following 2020 statistics are from Baseball Reference.

• Ryan Buchter pitched 6 innings with SO/BB of 1.33 and an ERA of 4.50.
• Humberto Castellanos pitched 10.2 innings with a 2.40 SO/BB of and an ERA of 6.75.
• Tyler Clippard pitched 26 innings with a 6.5 SO/BB and an ERA of 2.77.
• Stefan Crichton pitched 26 innings with a 2.56 SO/BB of and an ERA of 2.42.
• Chris Devenski pitched 3.2 innings with a 1.67 SO/BB of and an ERA of 14.73.
• Riley Smith pitched 18.1 innings with a 3.6 SO/BB of and an ERA of 1.47.
• Joakim Soria pitched 22.1 innings with a 2.4 SO/BB of and an ERA of 2.82.

The last two bullpen roles will be long relief as follows:

• Taylor Clarke, 128 IP Majors, 510 IP other, 2.12 SO/BB, 5.44 ERA, 0.49 RAA/100p for changeup.
• Alex Young, 129.7 IP Majors, 448 IP other, 2.56 SO/BB, 4.56 ERA, 0.13 RAA/100p for changeup.

My 9-man opening day bullpen prediction:

• Ryan Buchter
• Humberto Castellanos
• Taylor Clarke
• Tyler Clippard
• Stephan Crichton
• Chris Devenski
• Riley Smith
• Joakim Soria
• Alex Young

Comparison to Roster Resource’s projection.

On 22 February (before Tyler Clippard was signed), Roster Resource (at FanGraphs’ website) projected a 9-man bullpen. Their projection included 5 different pitchers.

• Travis Bergen
• Kevin Ginkel
• Yoan Lopez
• Keury Mella
• Taylor Widener

Let’s look at the objective criteria for the 5 additional candidate pitchers:

Data from Baseball Reference and FanGraphs.

If I was given a choice of one of those five pitchers to add to my bullpen (making it a 10-man bullpen), who would it be? My comments in the AZ Snake Pit Roundtable were that Travis Bergen could have a breakout season, so it would be optimistically awesome to add him. His second best pitch is awesome. On the other hand, Kevin Ginkel has the lowest ERA and the highest SO/BB, with Yoan Lopez close behind. And Keury Mella is out of options which is a reason to pick him. Although right now I would pick my optimistic choice, the wisest choice would be to decide after seeing spring training games.

In summary, the bullpen competition is wide open. Opinions differ. Now you know my prediction. Who do you think will have a bullpen role on opening day?