Insights on Diamondback Relief Pitchers

Relievers had half-life of one year.

In February 2019, Jim McLennan wrote about the 20 Diamondbacks relievers. If we assume a half-life of one year, that would predict 10 of them would remain in February 2020, 5 would remain in February 2021, and 2.5 would remain in February 2022. The half-life assumption seems accurate because in February 2022, at most two pitchers (Ginkel and Crichton) will remain.

Another way to look at it, when did the Diamondbacks acquire the 28 pitchers who pitched in relief? Nearly half (13 of 28) were acquired in 2021. That’s what would be expected with a half life of one year.

Relievers can be grouped by how they were acquired.

For this season’s relief pitchers, the following pie chart shows how they were acquired.

2021 Season, games through 6 September. Data from Baseball Reference.

It is striking that acquisitions by free agency, trade, and waivers account for most acquired relievers. Two possible explanations:

• At the highest level of their farm system, the Diamondbacks lack talented pitchers. That will change as talented pitchers in the lower levels advance.
• The Diamondbacks farm system has not yet figured out how to develop pitchers at the highest levels. The Diamondbacks will gain that know-how as they follow pitchers who leave the organization and find success elsewhere.

The ERAs in relief had a wide range.

The following chart shows some of that range. It also is an early view of next season’s possibilities in the bullpen. ERA’s above 6.15 in relief are not on the chart.

2021 season, games through 6 September. Excluded Widener & Gilbert with less than 4 innings as reliever. Data from Baseball Reference.

The 20-50 rule applied.

Six pitchers (21%) accounted for 49% of innings pitched in relief. Interestingly, 4 of the 6 pitchers also started games. The following pie chart shows the percentage of relief innings they pitched.

2021 Season, games through 6 September. Data from Baseball Reference.

Four relievers played their first career year in 2021.

Although this season their performances are near average for the Majors, that is a good sign. I expect these pitchers will improve next season, in part because of their experience this season.

Brett de Geus. Remarkably, this season he jumped from A level minors to the Majors, skipping the between steps. In June the Diamondbacks acquired him on waivers from the Rangers.

His ERA improved from 8.44 with Rangers to 5.59 with Diamondbacks (through 10 September). One measure of relief pitching is got-the-job-done, defined as zero earned runs and zero inherited runners scored. His got-the-job-done improved from 53% to 56%. Data from Baseball Reference.

He is an extreme ground ball pitcher based on his 55% groundballs through 10 September. Demarcation for extreme from Rob Neyer, SB Nation article written in 2012. Data from Baseball Savant.

JB Bukauskas. He has a high ceiling. In 2014 the Diamonsbacks drafted him in the 20th round, and he chose to go to college. In 2017 The Astros drafted him at # 15 in the first round. He was traded to the Diamondbacks in July 2019.

His fastball velocity is at the 70th percentile and his fastball spin is at the 65th percentile Data from Baseball Savant.

Although in the minors he was mainly a starter, this season he was exclusively a reliever. This season through 19 September, his ERA was 7.79 and his got-the-job-done was 52%. Data from Baseball Reference.

Miguel Aguilar. In 2016, the Diamondbacks signed him as an undrafted free agent. In games through 10 September, his ERA was 6.75 and his got-the-job-done was 50%. Data from Baseball Reference.

Brandyn Sittinger. in 2016, the Diamondbacks signed him as a free agent. This season, his maximum exit velocity was 100.6 mph.

Baseball Savant showed the most similar player was Brandon Kintzler. Through age 36, Kintzler pitched 12 years in the Majors, 8 with an ERA+ over 100. At age 27, Brandyn Sittinger has potential for many years in the Majors.

Ten pitchers were starters & relievers.

Ten of the 33 relief pitchers (ignoring position players who pitched) were both starters and relievers. They are mixed relievers, with more than one pitching role.

“We haven’t established roles because we’ve had so many injuries and we’ve had a revolving door of success and failures that I’m trying to simply put guys in the right place to have that type of success.” — Torey Lovullo

Relievers have a new mindset.

My view is that it would be advantageous for the pitchers to have roles.

• The mindsets of starters are different from the mindsets of relievers. Starters pace themselves to last more innings, they use a wider range of pitch types (normally), and sometimes they pitch to contact to keep pitch count lower. They vary their approach so they can effectively face each batter more than once per game. Relievers are more about maximum effort and overpowering each batter.
• When a relief pitcher knows his role, during the game he can mentally and physically prepare to enter the game; he knows when he will enter, and he can anticipate the batters.
• Roles give the relief pitcher a sense of control.
• Roles give the relief pitcher a more defined sense of who he is as part of the team.

The other side of the coin is that Torey Lovullo is one of the few managers I would trust to make the most of pitching without roles.

“For me, it’s more a mind-set of making pitches, hitting your spots and executing at a very high level. When we do that, we have the right guys down there [in the bullpen].” —Torey Lovullo