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Closer Depth: Zach McAllister

Will he be called up to close games?

Zach McAllister.
Zach McAllister.
Photo by Adam Glanzman/MLB Photos via Getty Images


2018 MLB stats: 44 games, 39:10 SO:BB, 45.0 IP, 6.20 ERA, 4.47 FIP

2022 AAA stats: 56 games, 90:27 SO:BB, 67.2 IP, 3.99 ERA, 3.83 FIP

Date of birth: December 8, 1987 (35 years old).

2023 status: Minors Depth for the Diamondbacks (signed in December).

How did SB Nation writers see him?

For three seasons (2012-2014) Zach McAllister was a league-average starter in the back end of a rotation. For three seasons (2015-2017) he was a near-fireball reliever with a career high strikeout percentage. Near the end of a disappointing season (2018) he was designated for assignment. Quotes follow.

“I hate to be a pessimist but I’m doubtful his 2014 numbers will top last year’s production. I still think Zach will keep up his league-average levels of performance, retaining his value as a number four starter, but I think it’s unlikely he’ll go another step up the ladder and progress like Kluber and Salazar are scheduled to.” — Ash Day, SB Nation, March 2014

“Three times this century an Indians [Guardians] pitcher has allowed 9 runs in an inning, but they were never all earned, so 8 earned runs is the highest total. Given that McAllister matched that total, while giving up multiple home runs and issuing multiple walks, and is one of only two pitchers on this list who recorded only one out, I think McAllister’s 2nd inning last week is the very worst inning by any Indians pitcher this century.” — Jason Lukehart, SB Nation, May 2014

“McAllister is almost certainly never going to be a really good starter, but having looked at his numbers, I think he’s better than he’s looked during the last two and a half months, and I still think he can be a solid back-of-the-rotation starter.” — Jason Lukehart, SB Nation, August 2014

Jason Lukehart of SB Nation made a great suggestion that actually happened the next season. “[for 2015]…I tend to lean towards option B [put him in the bullpen]. I believe McAllister is a much better 6th [starter] option than most fans (or most LGT readers anyway) seem to think.” — Jason Lukehart, SB Nation, November 2014

“Pitcher Zach McAllister may have found his new home in the Cleveland Indians [Guardians] bullpen after posting a 2.49 ERA in relief during 2015. He made his fair share of mistakes over the season, but statistically this was McAllister’s best year by a longshot. It is no secret that McAllister is mostly a two-pitch pitcher. He has a curve and a cutter that he can throw, but his main strengths are his fastball that reaches 96-97 MPH and a changeup.” — Matt Lyons, SB Nation, November 2015

“He’s bumped his fastball velocity up to the mid-90’s since fully converting to the bullpen, hitting as high as 98.2 mph this year. This speed bump, which occurred in 2015 when he was able to go truly max effort every time out, has led to a leap in strikeout rate. Prior to moving to short relief his highest strikeout rate was 20.3 percent. Since 2015 that number has been 28.1 in 2015, 23.2 last year and now 29.0 percent in 2017. Aside from the improved velocity, this year in particular he’s gone back to what made him a major league prospect in the first place.” — Merritt Rohlfing, SB Nation, June 2017

“There was a time not too long ago when Zach McAllister seemed to have turned a page. Pretty much through the All-Star Break, he looked excellent. He was striking out a career-high 29.5 percent of hitters, owned a 2.56 ERA, and was showing renewed command in his curve ball. But since the break he’s been much more like the McAllister of old, It must be wondered what happened to a man who looked to making a case for being the new Bryan Shaw….I don’t know if he’s a bit hurt, or has a small blister or some other hand problem that doesn’t allow him to throw the curveball, but McAllister has lost all his effectiveness [without it].” — Merritt Rohlfing, SB Nation, September 2017

“To make room for Miller, the Indians will designated Zach McAllister for assignment following another disappointing campaign out of the bullpen. The 30-year-old has a 4.97 ERA in 41.2 innings this season with a strikeout rate that is lower than it has ever been as a full-time reliever.

I’ve always had a bit of a soft spot for McAllister — especially when he was on the verge of being a fire-balling reliever — but he never put it together for the Tribe. Far from a total trainwreck, but an extremely volatile commodity in the bullpen.” — Matt Lyons, SB Nation, August 2018

2022 Review.

Pitching in AAA, Zach McAllister improved in 2022 compared to 2019 and 2021. The following table shows his improvement in reducing home runs and his improvement in FIP.

Data from FanGraphs.

Comparison of Zach McAllister and closer Mark Melancon. After talking about each factor, the comparison will be shown in a table.

A basic comparison is average fastball velocity in 2022: McAllister’s 93.0 MPH was better than Melancon’s 91.7 MPH.

The important comparison is the big three: strikeouts per batter faced, whiffs per pitch, and balls in play and homers per strike. Mc Allister was better in all three statistics, whether we compared his 2018 season in the Majors or compared his 2022 season in AAA. His AAA season was amazing because he met my big three criteria to be included in the rebuilt bullpen (for details see this AZ Snake Pit article).

The projected FIPS are too close to say either is significantly better than the other. Both projected FIPS are below league average.

The next comparison is home runs per fly ball. In 2018 McAllister’s HR/FB rate was a career worst, and it marks his transition to the minors. Although McAllister improved his HR/FB ratio to 11.5%, it is not as good as Melancon’s 8.3%.

Because the likely role of these pitchers is closer, how often they got-the-job-done (GTJD) is important. Got-the-job-done means no runs scored (earned or unearned) and no inherited runners scored. Last season, McAllister’s GTJD was better (AAA 64.3% vs 62.9%). Nevertheless, it’s unclear who would be better – perhaps spring training would add clarity. Previously, I defined 67.7% GTJD as the minimum for a reliable closer. Both closers fell short of that ideal.

Data from Baseball Reference, FanGraphs, and Brooks Baseball.

Overall, Zach McAllister compares favorably to Mark Melancon in the statistics shown in the table. Mark Melancon’s strength is fewer home runs per fly ball.

Zach McAllister is the type of pitcher who would fit in the Diamondbacks rebuilt bullpen because last season’s excellent performance in statistics shown in the table, especially strikeouts per batter faced, whiffs per pitch, and balls in play plus homer runs per strike.

One additional comparison is experience as a closer. Melancon has much more experience as a closer (454 vs 54 games ‘finished’ in the Majors, 79 vs 33 games ‘finished’ in the minors). An important decision for the Diamondbacks is whether statistics or experience is the better indicator of future performance of a closer.


Overall, Zach McAllister compares favorably to Mark Melancon. Nevertheless, Melancon has more experience closing games and has perhaps earned the right to start the season as closer.

A likely path forward is that Melancon will start the season as closer and at some point (due to injury or ineffectiveness) McAllister gets called up to show how well he can close. Some statistics show his results would be at least as good as Melancon’s results.