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Rotation Candidates for the 2022 Diamondbacks

Candidates’ stats are compared to averages. Four role models are suggested.

Carson Kelly, Matt Herges, and Zac Gallen.
Carson Kelly, Matt Herges, and Zac Gallen.
Photo by Chris Coduto/Getty Images

The Diamondbacks played winning teams in September (more details about September opponents can be found in Picking Position Players for 2022 Diamondbacks). Nine potential starters for 2022 pitched in September (7 as starters, and 2 as relief appearances only). After we choose which stats to look at, let’s compare their September stats to averages in the Majors.

  • ERA and GameScore. These two stats are basic ways to measure performance
  • Fastball velocity and strikeout percent. I tip my hat to Jack Sommers for bringing up the issue of fastball velocity and strikeout percent. On 2 October, he pointed out that Diamondbacks starters ranked 27th in fastball velocity and 23rd in strikeout percent.
  • Homers per 9 innings and swinging strike percent. In a semi-transparent way, as he talked about the Diamondbacks, Mike Hazen made me realize these stats are important. One view is K% in September. For the four players who started at least 4 games in September, their best K% in a 4-game streak was compared to streaks in all teams
  • Pitch efficiency impacts how many innings the starters pitch, and that impacts the workload on the bullpen. Three measures of efficiency are: pitches per batter faced, batters faced per inning, and average strikes per pitch.
  • BABIP is an important stat because my belief is that next season’s defense will be much improved, and that better defense will positively impact our starters’ performance. In other words, those pitchers with the highest BABIP will see the most improvement next season.
  • Percentage of hits that are ground balls. This impacts HR/9 and allows bigger defensive impact.

Comparing Candidates to averages in the Majors.

Pitchers who started in September plus Widener & Smith. 1 to 30 September. Data from FanGraphs, streaks from Baseball Reference, game score average of FanGraphs. Baseball Reference, and methods. Averages in Majors were subjectively determined for example ERA average was LAA SP average because their SP was ranked 15th in the Majors.

The following table shows which pitchers were above average, or nearly above average in September. The three pitchers who were in the table most frequently were Gallen, Gilbert, and Weaver.

Pitchers who started in September plus Widener & Smith. 1-30 September.

Pitching Role Models.

In my mind, each pitcher has a role model. Each pitcher strives to become as good as or better than his role model. When each pitcher improves towards his best self, his stats become more like his role model.

Although I’m oversimplifying and arguments could be made for different role models, I picked four role models for the Diamondbacks rotation. Looking largely at three characteristics FB/GB, high strikeouts/low strikeouts, and stuff/no stuff, and placed the nine candidates with their role model.

2004 Randy Johnson. Randy Johnson entered the Hall of Fame as a Diamondback. He won the Cy Young 5 times, the ERA title 4 times, the triple crown, and World Series MVP. The 2004 season was appropriate because like 2021, the Diamondbacks’ win-loss record was historically bad. That season when Randy Johnson pitched, and the Diamondbacks scored at least 3 runs (see The Wonder of Positive Streaks), they won 13 of 18 games - great for that 51 win season!

What about Randy Johnson could Zac Gallen strive for? Increase his K%, especially by swinging strikes. Every small step towards pitching as great as Randy Johnson would be difficult and impressive. Zac Gallen has potential for greatness.

2020 Jake Arrieta. Jake Arrieta won the Cy Young in 2015. My view is that his strength was his flexibility to to throw his best pitches over different parts of the plate. That meant that he could place those pitches where hitters who were swinging for the fences would not find much success. For more about Arrieta, see this AZ Snake Pit article.

Merrill Kelly, Luke Weaver, and Humberto Castellanos need to reduce their Homers per 9 innings. My view is that the answers can be found in study of Jake Arrieta.

2018 Justin Verlander. Justin Verlander won the Cy Young twice, the ERA title, the Triple Crown, and the ALCS MVP. His strength was fly balls were hit softly - average exit velocity on fly balls was 90.1 mph per this SB Nation article. And 39.8% of contact was made under the ball causing too-high launch angles.

My view is that Taylor Widener and Caleb Smith, with few batted balls as grounders, could benefit from study of Justin Verlander.

2021 JA Happ. JA Happ pitched well in the 2016 post season. His 15 seasons in the Majors is strong evidence that his pitching is fundamentally sound.

Tyler Gilbert, Madison Bumgarner, and Mejia could continue to focus on the fundamentals by study of JA Happ, and thereby extend their years in the Majors.

Data from FanGraphs, Baseball Reference, and

Picks for the Opening Day Rotation.

My picks will almost certainly change before the season starts. The Diamondbacks expect their pitchers to improve in the offseason, and trades could have big impacts.

Let’s be bold! My picks follow:

  • Zac Gallen
  • Tyler Gilbert
  • Luke Weaver
  • Taylor Widener
  • Madison Bumgarner