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Of Prospects and Rosters, Part III: Pitching (upper minors)

While pitching is the strength of Arizona’s farm system, much of it is still a fair distance off.

San Francisco Giants v Arizona Diamondbacks Photo by Norm Hall/Getty Images

In this part, the examination shifts to Arizona’s pitching prospects. Pitching is this farm system’s strength. That shouldn’t come as a surprise for anyone. Other than 2017, when Mike Hazen first came on board, and during a time he openly admits he was not as prepared for the draft as he would have liked, Arizona’s drafts have been pitcher heavy at the top. 2018 saw the Diamondbacks make six of their first nine signed picks (six of ten overall thanks to the Matt McLain affair) come from the pitching ranks. In 2019, it was six of 10 picks, including selections 2-6. In 2020, it was four out of five total picks in the draft. Three of those four are already making waves. When looking at the few position players which were selected above or among the pitchers in those three years, the players that one sees are Jake McCarthy and Corbin Carroll. Both of those players were touched on in part two of this series as having potential good value for this franchise, with McCarthy two months from essentially awaiting injury or trade to get a shot at the Majors.

When evaluating things like “upside” and “potential MLB impact”, or any of a host of other scouting catchphrases that get applied to young developing talent, the lion’s share of it rests in Arizona’s pitching. Depending on which list one chooses to use, one will find as many as seven of Arizona’s top 10 prospects come from the pitching ranks. If one expands that list to the top-20, the numbers stabilize some. The order may change but mostly, right around 15 of Arizona’s top-20 prospects are pitchers.

Of course, not all of those pitchers are in the upper minors. In fact, very few of them are.

Corbin Martin (AAA)

Corbin Martin remains one of the organization’s top-upside prospect pitchers, despite his troubles. And woah Nellie, have there been some troubles. A more thorough profile of Martin can be found here. And, for those who are interested or need a refresher, coverage of his struggles can be found here, written up by Jack Sommers.

Martin may be the current poster child for the issues with Arizona having its AAA affiliate in Reno. While in Reno, Martin’s control problems persisted - sort of. What’s more accurate is that Martin’s walk problems persisted. The control on the other hand, was fairly evident. Martin’s outings, painful as some were, showed composure and an understanding of the game plan, which included him working on attacking the bottom of the strike zone more. His breaking pitches and his change-up both, continued to get him in trouble. Pitches continued to miss a bit high, which is not a good thing for a change-up. The curveball, which used to have a pronounced arc, is lacking some of the late break it once had. What Martin was doing consistently though, is missing in the same spots over and over again. Martin is throwing the pitches he wants and he is getting very consistent results in the same places from his pitches. What he is not getting is consistent good results. This is one place where I agree with Mr. Sommers. It might be best to send Martin all the way to Amarillo and let him work out his problems in AA. There, his change and his curve should both respond in the expected manner. Then, if/when he finally gets his mojo back (and hopefully a tick or two of velocity now that his arm is getting stronger), let him go from Amarillo to Phoenix.

Martin’s debut outing for Arizona was much better than his stat line shows. The majority of the damage was done on the last few pitches of his outing. Martin’s ceiling remains that of a solid rotation contributor. At the very best, he’s a #2/3 type starter. More likely, he is a solid, innings-eating, league average pitcher. Those are far more valuable than they get credit for. He’s going to need to refine the shape of his pitches and find the strike zone more regularly in order to reach those levels though. Expect to see more of him this season. There are still three months of games left and the Diamondbacks have precious few options to help get them through.

J.B. Bukauskas (MLB)

It depends on who you ask. Some will tell you that Bukauskas has the stuff to be a dynamic middle-of-the-rotation starter. Others insist his frame will never hold up to that level of work load and that he is a high leverage reliever. For what its worth, the Diamondbacks have already made up their minds. Early this year, they told Bukauskas he is a reliever - period. Of course, that could change if he gets traded. However, the Diamondbacks have little reason to consider doing that. So, Bukauskas needs to be viewed through the lens of being a relief pitcher. Coming into the season, Arizona bent over backwards looking for ways to avoid promoting Bukauskas. Once he finally got the call, he did not fail to impress during his first four outings. Then, during his fifth outing and for the first time since 2019, he got hit. That seemed to rattle him a little bit. After that he was somewhat inconsistent, alternating good outings and not-so-good ones. And arm injury sidelined him and he has only just now returned to duty. His first outing was a bit of an adventure, one in which he was a bit unfairly tagged with results that were worse than his pitching. He managed to walk three batters and allow a grand slam home run. That’s ugly. What isn’t in that stat line is the fact that he induced a double play and a grounder to end the inning, but that the grounder was thrown away, which extended the inning, allowing that big fly to kill his outing entirely before he induced yet another grounder to finally end it all.

Bukauskas is going to get an awful lot of groundballs and strikeouts. He has shown in the past that he has the stuff to succeed at the top level. He still profiles as a high leverage reliever. His success is going to be linked to his ability to control the walks, which is the biggest knock against him sticking as a starter, so it should be no surprise that the control part of his game is still a work in progress. Despite his struggles, Bukauskas’ good outings outnumber his bad ones and he is already making MLB hitters look silly.

Humberto Mejia (AAA)

In Part I, I promised an opportunity for nay-sayers to have at me regarding Mike Hazen’s trades involving Starling Marte. Well, that time has come. Even though the way in which Mejia has arrived in Reno has almost nothing to do with his status as a premium pitching prospect, it is almost impossible to discuss him without the “what might have beens” coming out of the woodwork. So, before I get into too much about Mejia, I will take this moment to discuss the Starlin Marte trade saga.

Before the pandemic struck and changed absolutely everything, the Diamondbacks went into “win now” mode. They traded glove-first SS prospect Liover Peguero and heralded pitching prospect Brennan Malone to the Pittsburgh Pirates for veteran center fielder, Starling Marte. It was a steep price, but one has to give quality to get quality. Neither player given up had risen as far as A+ ball and, despite being prized prospects, neither one was a blue chip type prospect. Then, the pandemic struck. Everything changed, including the outlook for the team and the team’s finances. This created a chain of events that saw Arizona turn around and trade Marte to the Miami Marlins. The return was Caleb Smith, a left-handed MLB starter, and Humberto Mejia, one of Miami’s prized pitching prospects who saw his service time accelerated by the pandemic. Mejia, after dominating A+ ball, was called upon to start games for Miami as the result of Miami’s entire organization being torn to pieces by COVID-19. He only needed to make three starts and managed to pitch to a 5.40 ERA while turning in 10 full innings of work. Given he jumped from A+ to MLB with no chance catch his breath, it is okay to forgive him for stumbling to an 87 ERA+ over those outings. It’s a small sample size and he wasn’t even supposed to be there in the first place.

Since then, Mejia has taken the challenge of pitching through the minors to heart. He dominated at the AA level and has recently been promoted to AAA-Reno. There, he has had two decent games, three or four times where he was blasted, and one very impressive outing.

Thus net result of the Marte trade was Liover Peguero and Brennan Malone for Caleb Smith and Humberto Mejia. Mejia has every bit the upside Malone does, with the added benefit of having already made the difficult transition through the jump to AA. He is also starting to show promise in AAA, giving every reason to believe he will indeed be returning to the Majors, potentially as early as this season. Peguero has made the transition to A+ ball for Pittsburgh and seems to be handling the change well enough, though his plate discipline has taken a hit. Meanwhile, Caleb Smith is maturing from a scrappy left-handed starter into a real bulldog and is showing that there is every reason to expect that he will stick as a MLB-caliber starter. The present value of the return from the second Marte trade matches up against the potential future value of the prospects traded away to obtain him in the first place. Given that Arizona’s front office had no choice but to cut Marte’s salary (and the world knew it), getting back full value is something to be admired.

Tommy Henry (AA)

When people talk about a strike thrower, Tommy Henry is the sort of pitcher they are talking about. Henry is a somewhat unheralded prospect selected 74th overall in the 2019 draft. He has no real outstanding tool. He does, however, tunnel his all of pitches well, which allows all of them to play up above their true level. He also is not afraid to attack the zone. Still his walks have elevated a bit since he began starting games in Amarillo. Currently, his walks are a bit over four per nine innings. That’s not ideal for a starter, but it is by no means an insurmountable issue to overcome. On the other hand, his tenacious attacking of the zone has also resulted in a gaudy 11.31 K/9. Given the current state of affairs on the MLB roster, there is no reason to rush Henry’s development. The team has every incentive to let him continue developing as a starter. Barring injury, he should be in AAA by the end of the season and be looking for a taste of the Majors as soon as next year. However, should the organization decide to pivot from that approach, Henry has the stuff to be a reliever at the MLB level already, potentially even a high-leverage one.

Henry is yet another mid-rotation arm with a low-to-mid 90s fastball. His fastball, change-up, and slider all rate as average or better and his control rates as solidly above average. He is unlikely to blow away the competition when he finally arrives, but he is one of those that there is little doubt he will arrive.

Mack Lemieux (AA)

If Lemieux ever gets his walks under control, he’ll be throwing high-leverage relief for years to come. Walks were never an issue before this season. Of course, this is also the season Lemieux made the difficult jump to AA. The result of that jump has been a mixed bag. His walks went from a very controlled number around 3 BB/9 to over 6 BB/9. On the other hand, his already prodigious strikeout numbers absolutely exploded. He is now striking out 13.50 K/9. The sample size is starting to become meaningful as well (for a reliever), 20.2 innings across 17 appearances. Lemieux may well end up flaming out after being tried in middle relief in a year or so. Or, he may find his control again now that he is getting accustomed to the more difficult level of hitting he is up against. That puts his ceiling as a high-leverage reliever/closer of the old-fashioned “strike them all out” variety.

Unfortunately for the Diamondbacks, that just about does it for prospect pitchers in the upper minors. On one hand, there is some solid quality to be found there with some very appealing upside. On the other hand, as has been repeatedly pointed out as fans start scouring the farm system looking for an answer to Arizona’s losing ways, this selection is decidedly lacking in any sort of high impact arm. Corbin Martin rates as having the highest potential impact, but even that still leaves him the second or third best arm on most MLB pitching staffs.

Josh Green

Despite his recent run of success in Reno, Josh Green is almost certainly a future reliever. His ERA is well below expected levels. Those expected levels are unlikely to ever come down because he simply does not strike out many batters. That’s the bad news. The good news is, he doesn’t walk hitters either. Green features a traditional four-pitch mix of fastball, slider, curveball, and change. All of them are relatively average offerings. His control is well above average, as is his tenacity. Like Caleb Smith, he tends to simply go to work, fill the zone with pitches, and then lets the results pan out. He doesn’t try to get fancy. He does not surprise hitters with a ton of gar up in the zone just when they think they are locked in. Like Matt Peacock, currently a member of the AZ bullpen, Green is an extreme groundball pitcher. This has been a huge asset for him in Reno and will only continue to serve him well once he reaches the Majors. Arizona is in no hurry to tweak Green’s development, content to let him continue starting games in AAA. He should be promoted to the Majors at some point in 2021 though, where he will almost certainly settle in as a middle reliever.

How They Stack Up


The Dodgers are known for having what seems to be a constant supply of arms ready to dominate the Majors. Well, those arms are not in the upper minors just yet. While Josiah Gray (#55 overall prospect in baseball) was just promoted to AAA, the rest of the Dodgers pitching prospects in the upper minors are few and far between and all of them are of the relief variety, likely middle relief. Gray is still a full year away from being ready, though Dodger pitching injuries might see that timetable accelerated to September of this year.

Outside of lefty Sam Long, who recently debuted for the Giants, the only other pitcher of note San Francisco has is Sam Hjelle, down in AA. Injuries forced the acceleration of Long’s development. After starting the season in AA, he has pitched in AA, AAA, and MLB already, and it is only July. He profiles as a fringe starter/reliever. He would find a home at the end of a number of rotations. On the other hand, he’s a middle reliever for teams with strong rotations. Hjelle profiles as only slightly better and is currently working the slow and steady development route in AA.

If there is one place that San Diego still has some prospect depth, it is in pitching. Ryan Weathers has acquitted himself with flying colours since debuting this season. He appears to be ready to stay in the San Diego rotation for the long haul. The other pitcher of note is San Diego’s top prospect, MacKenzie Gore (#10 overall). Gore was just recently promoted to AAA. The results have not been stellar. On the other hand, he just got there. Despite losing a year of development to the pandemic, Gore is still a full year ahead of schedule in his development. Yes, he is a prospect to be on the lookout for and is the sort that Arizona wishes it had in the upper minors. As bad as things became under Tony La Russa, they never became bad enough for the Diamondbacks to get the third pick in the draft.

The rest of the Padres upper minors prospect pitching is entirely relief-based, some of it having already debuted for the Friars. None of it profiles as meaningful or high-leverage.

Seriously, I don’t know why I even bother listing the Rockies in these reviews, other than perhaps to show just how bad things could get. It gives Arizona fans a chance to be thankful for the organization they have. After all, things could be worse. Things could look like they do for the Rockies.

Not one pitcher of note in the upper minors, reliever or starter.

TL/DR Recap

While the strength of Arizona’s farm is in its pitching, the best of that is still a ways off. Though Arizona has a few arms in the upper minors worth noting, they lack the big impact arm that some systems, including San Diego possess. As for the Dodgers, Giants, and Rockies, the Diamondbacks actually stand up rather well when comparing prospect arms in the upper minors. In a great world scenario where all the prospects click, the 2023 rotation could feature Zack Gallen, Corbin Martin, Humberto Mejia, Caleb Smith, and Tommy Henry. While that rotation is unspectacular, it should eat innings in bunches and do an admirable job of keeping the team in games. While not a stellar starting five, it is a massive upgrade from the current dumpster fire of a rotation the Diamondbacks are running out at the top level. Of course, there is a real possibility that the above rotation will fail to materialize due to injury or one or more of the arms simply not making it all the way. But, at least the cupboard is not completely barren. In fact, it might have just the right amount of talent to see the team through until the arms behind those listed arrive, those in the lower minors, where the real talent lies.

Up next: Part IV: Pitching (lower minors)