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2023 Diamondbacks Reviews: #38 Justin Martinez

Great velocity requires great accuracy.

Arizona Diamondbacks v San Diego Padres - Game Two Photo by Sean M. Haffey/Getty Images
  • Rating: 3.75
Justin Martinez’s Rating breakdown
  • 2023 stats: 10 G, 10 IP, 12.60 ERA, 6.96 FIP, 2.40 WHIP, 1.27 SO/BB (12.6 K/9, 9.9 BB/9), 36 ERA+, -0.5 bWAR.
  • Date of birth: July 30, 2001 (22 years old)
  • 2023 earnings: $116,130 (via Spotrac)
  • 2024 status: On 40-man roster, Pre-Arb., 2 options remaining.


If fan hype could guarantee you a roster spot at the beginning of the season, then Justin Martinez would have become a slam dunk entry on the Opening Day roster.

“Justin Martinez is pretty awesome too, that is heat esquire he launches. I can see why they protected him. If it weren’t for the lack of AAA experience I’m sure he’d be a lock for this year’s bullpen on opening day.” - DBacksEurope in an AZSnakePit Round Table on March 13, 2023 when asked about “Pick a player who has stood out during Spring”

“Justin Martinez by far. Seems like every time he’s pitching, my Twitter timeline is blowing up with people talking about how hard he is throwing.” - ISH95 in an AZSnakePit Round Table on March 13, 2023 when asked about “Pick a player who has stood out during Spring”

While we were still a bit conservative on this site, on other sites commenters were less reserved. ISH95 mentions Twitter, but on MLBTR you could also find voices that were convinced Justin Martinez deserved to be part of the active roster.

You really can’t blame the fans. It is hard not to be excited about Justin Martinez and his triple digit fastball considering the amount of soft tossers we have had in the bullpen the last...10 years? Except for a bit of Yoan Lopez we have disappointingly seen Mike Hazen pass on flame throwers while every other self-respecting top team always have seemed to have at least one of them in the bullpen.

Looking back, Justin Martinez didn’t need much time to establish himself within the list of the better prospects in Arizona. The Dominican native was a very low-profile international signing in 2018. He didn’t sign until March 2018 and did so for what could be a minimum amount: 50k. It might be that most teams didn’t have the kid from Bonao on their radar, because he had apparently just converted to pitching right before being signed. That was obvious in his first season in the Dominican Summer league where he struggled to a 7.57 ERA, allowing more walks than achieving strikeouts.

But in 2019 he almost doubled his strikeout rate in the Dominicana with a 12.2 K/9. He found himself soon overseas in the complex league and even got a taste of more seasoned ball in Missoula. In 2020 he was at instructional camp where he apparently confirmed his 2019 progression and in 2021 he unanimously hits the prospect lists in the USA.

In 2021 Justin Martinez starts the season in Visalia with mixed results and after just 7 appearances he is set for TJ surgery, wiping out his entire season. He returns to action mid 2022, as a reliever, and is assigned to Hillsboro, but ends the season with a handful appearances in both Amarillo and Reno. The 14.7 K/9 in 2022 is impressive, but also combined with a 5.2 BB/9. However, the fastball velocity is still there, which is probably the best news after returning from TJ.

That awesome velocity is showcased in Spring Training 2023, but with just 38.0 innings under his belt in 2022, the 21-year old is probably best off with a bit more seasoning at Reno.

2023 review

When Justin Martinez was called up to the major leagues on June 27, there was obviously some vibe because of the triple digit fastball. At that moment his ERA might have been frowned upon, but news outlets correctly pointed out that it was heavily skewed by the first 5 appearances of the season in Reno, in which he gave up 12 runs in 4.2 innings, walking 11 batters as well. A wild, wild beginning of the season.

In the following 23.1 innings, before his first call-up, he had allowed just 3 runs and no homeruns, although with 16 base-on-balls he was far from being impeccable.

That stretch of success also gave a bit more insight in the pitcher Martinez is: despite the heat he brings, the fastball isn’t a pitch that blows batters away. In those 23.1 innings in Reno he achieved a 65% ground ball percentage, while the strikes looking and swinging barely passed the 15%.

2022 saw him develop a very highly-valued splitter, that FanGraphs has ranked as 60/70. Indeed, he was incredibly effective with that splitter in the MLB, limiting batters to just .083. Another good secondary offering was his slider, not valued that well by watchers, but successful in the majors, with a .167 batting average against. He got a whiff-percentage of, more and less, 50% on both of them.

The problem in the majors was exactly that triple digit fastball. When located well and combined with the secondary stuff, Justin Martinez had no troubles and getting batters out. We saw some great examples of what his well-located fastball is able to accomplish.

But, on the other hand, when his fastball was off, batters had no troubles in waiting for either the walk ...

... or the meatball.

His fastball had a shocking .440 batting average against with a .760 slugging percentage. That totally wipes out the initial excitingness of Martinez becoming the first Diamondback rookie to hit over 100mph consistently in his debut.

And so, his results in the MLB were rather salty. After not debuting at the end of June he was optioned and then called back up a week later. Although most outlets rather focused on the velocity, his debut wasn’t successful with 2 runs against. The next two outings were “scoreless”, although inherited runners did cross home plate. He wrapped his first stint in the majors up with a 5 run outing against the Reds, where Matt McLain hit a grand slam. He was optioned to Reno the following day.

His return in August was comparable, although he started better with a save and 3 scoreless appearances until he gave up 2 against the Rangers and was then demolished once again by the Reds, giving up 4 runs in 0.1 innings.

Martinez then returned to the majors again to pitch in October against the Astros but once again wasn’t able to put up a 0.

2024 outlook

So, it was a lot of sweet and salt for Justin. Everyone can see the potential, but the biggest thing holding him back right now are the control issues. FanGraphs mentions that Martinez has closer potential if he can improve his command. Some have mentioned a 60% strike percentage as a reference. In 2023 he sat at 56% in the majors.

In Yoan Lopez we have a great recent example of how short-lived success can be when you have velocity, but not much more. Yoan threw quite hard (96mph), but wasn’t able to throw strikes consistently and apparently his fastballs were too flat. Justin Martinez isn’t that far from Yoan Lopez with his fastball quality and whether he can have more success than him remains to be seen, but the first thing the right-hander will need to work on is his command. That will be quite the challenge, because the track record isn’t great, but Justin still has time on his side, as he will be 22 years old coming into the 2024 season.

Unless he really shows a very much improved command in Spring Training, most likely Justin Martinez starts the season in Reno. His performance there this season shows he really doesn’t have too much left to do there and he could become another Luis Frías, who hangs a bit between AAA and MLB for a few years until he enters a now or never season. Because of the potential, the Diamondbacks will ride out his options until he has none left or maybe he becomes part of a trade to haul in a more established piece.