Going Deep: Is Merrill Kelly 2019’s Miles Mikolas?

Alex Fast takes a look at Arizona Diamondbacks pitcher Merrill Kelly to see if he can be the fantasy breakout Miles Mikolas was in 2018.

A few days ago in our Discord channel – which if you haven’t joined, you should, if not solely to get the information this article provides weeks before it’s published – Nick Pollack said the following:

The name Merrill Kelly has popped up on my radar once or twice in the past month. I knew he was likely going to fill the 5th rotation spot for the Arizona Diamondbacks. I also knew he played the past couple of years in South Korea. To be honest though, his name just sort of fell into the mix of back-end rotation guys. To see Nick get this excited about him though? I figured he may be worth a deeper dive.


The Origin Story


Drafted by the Tampa Bay Rays in 2010, Kelly spent four years working his way through the Rays minor league system. In 2014, Kelly was primarily being used as a swingman in AAA, where he put up the following stats:

28 15 114.0 8.53 2.92 0.69 22.2 7.6 2.76 3.74 1.26

Despite those solid numbers, the Rays were hesitant to place Kelly on their 40-man roster. Despite any opinions I have about why the Rays didn’t give Kelly a shot at the big league level (his 88-90 mph fastball may have been a reason), the fact remains that Kelly wanted to be a starting pitcher and the Rays viewed him more as a long reliever. So when the SK Wyverns of the KBO came calling and said they’d be willing to give him that opportunity, Kelly took the chance. Here are Kelly’s stats from his three years in the KBO:

Season GS IP K/9 BB/9 HR/9 K% BB% ERA FIP* WHIP
2015 29 181.0 6.91 2.69 0.80 17.9 6.9 4.13 3.73 1.34
2016 31 200.1 6.83 2.70 0.67 17.9 7.1 3.68 3.61 1.32
2017 30 190.0 8.95 2.13 0.76 23.2 5.5 3.60 2.97 1.31

*These are imperfect and are +/- about .25 of a run.

When I look at the data, a few important things pop out at me:

  1. I think we can chalk up the 2015 season to Kelly making transitional adjustments. The KBO has a different ball with different seams, not to mention that Kelly was playing baseball 7,500+ miles away from where he’d spent the past four years. Certainly being uprooted like that will have a negative impact on your on-field performance.
  2. Kelly was a workhorse. He finished 9th, 4th, and 3rd in IP respectively.
  3. The KBO widened its strike zone in the 2017 season. While that should in no way fully write off the success Kelly had in the 2018 season, that may have led to a few additional strikeouts.
  4. He seems to have made an adjustment somewhere that allowed his strikeout rate to jump.

After some research, I found out what that adjustment was- or at least the result of it. Kelly’s fastball velocity jumped from 88-90 to around 92-94 and peaked at 96. When asked about the spike in velocity, he said, “I wish I could put my finger on what exactly contributed to the spike […], but honestly, I don’t have a solid answer for you” (source). Along with the increased velocity, he also started attacking hitters a bit more and the swing-friendly KBO kept whiffing.

The Diamondbacks took notice and now Kelly is finally going to get his shot in the bigs as he’ll more than likely be the D-Backs #5 out of spring training. Let’s take a look more specifically at what the D-Backs can expect from Kelly’s arsenal.


The Arsenal


Four-Seam Fastball

Kelly’s arsenal centers around a fastball that sits between 92-94 mph and can occasionally touch 96. The righty spots the pitch fairly well, as he can elevate it when he needs to and also hit both sides of the plate with some consistency.


Two-seam Fastball

The two-seam features some slight arm-side run to it and comes in between 89-91 though an exact reading has been difficult to find.

*Apologies for the brevity of this GIF. There isn’t much to work with and figured this was better than nothing.


Circle Changeup

The circle change is arguably Kelly’s best pitch. It frequently starts near the heart of the plate and ends up down and in at the knees of right-handed batters, coming in around 8-10 mph slower than his four-seamer. It also seems to be his most consistent, as I’ve seen it used across all three seasons in the KBO.



Kelly’s slider sits around 85-87 mph and seems like a solid strikeout pitch with an above average amount of bite to it.



The curveball comes in around the low 80’s and seems to be the piece Kelly struggles with most command wise. For every curve I saw him bury in the dirt, I saw one or two he either left over the plate or missed with completely. Even scarier? I saw a heck of a lot more of the former than the latter. If there’s going to be a pitch that I think major leaguers are going to punish, it’s going to be that curveball.

Overall, Kelly sports an impressive arsenal that I see generating a good amount of K’s at the big league level.


Is Merrill Kelly 2019’s Miles Mikolas?


Any pitcher coming from overseas in 2019 is going to draw some comparisons to Miles Mikolas. While Mikolas pitched in Japan, Kelly pitched in South Korea in the KBO, a league more known for its power displays and bat flips. While the two do carry similar arsenals, they are utilized a bit differently. Mikolas primarily relies on his curveball and four-seam with two strikes, gets a ton of whiffs on his slider and curve and isn’t afraid to use that fastball when ahead. I’d expect Kelly to get a majority of his whiffs with his slider and change as I don’t think the curveball will be anywhere near as successful as Mikolas’s. If, however, Kelly is able to use that curveball effectively then he could be extremely effective, but that’s a big if. At the end of the day I think Mikolas has the higher overall ceiling while Kelly has the higher K upside.

So is Merrill the new Mikolas? Yes and no.

No in that I don’t think Kelly has the same ceiling, his ERA should sit in the high 3’s and I’d be surprised to see a sub 6% BB rate.

Yes in that Kelly is what Mikolas was coming in to fantasy drafts in 2018: an SP you can take at the very end of your draft who has some risk, but a higher upside than a lot of the guys going around him. As of my writing this, Merrill Kelly is the 443rd player and the 182nd pitcher off the board (including RP’s). Kelly is going behind Clay Buchholz, Joe Ross and Drew Smyly: just a few guys I would rather have Kelly over.

Overall, I think Kelly has the upside to be a #3, but is realistically a number 4. His ability to eat innings paired with the fact that the only person in Arizona biting at his heels is Matt Koch leads me to believe the organization will give Kelly a solid look. If you’re still not sold, keep an eye on him at spring training to see how his stuff fares but if you’re draft is coming up soon, Kelly is a really nice buy-low, high-upside pick.

Alex Fast

An FSWA award winner for Research Article of the Year, Alex is the co-host of On The Corner and host of the weekend edition of First Pitch. He received his masters in interactive telecommunications from NYU's ITP. All opinions are Alex's and Alex's alone. A die-hard Orioles fan, Alex is well versed in futility and broken pitching prospects.

7 responses to “Going Deep: Is Merrill Kelly 2019’s Miles Mikolas?”

  1. Nick Gerli says:

    Great article Alex! I didn’t know about Kelly beforehand so he’ll definitely be on my radar at the end of drafts.

    I love the effortless and almost casual delivery he has on his fastball.

    Was he injured in 2018? Can’t find stats for last year.

    • Alex Fast says:

      Thanks for reading, Nick! He was in South Korea last year. You pointed out a nice error actually. Looks like B-Ref has his seasons as 2015, 2016, 2017 for last year when they should all be a year moved up as he did pitch for the Wyverns last year. Thanks for the find!

  2. Derek Rhoads says:

    Another benefit to Kelly is I believe he has a clause in his contract where he cannot be assigned to the minor leagues without his consent. Helps with the job security

  3. Dominic Lozano says:

    nice article Alex, if all goes well for kelly for the first half do you see the diamondbacks flipping him at the deadline? ( expecting the dbacks aren’t contending). This might bring some more upside to his fantasy value down the road.

    • Alex Fast says:

      Thanks for reading! Maybe. He’s only on a two year deal. I doubt they’ll be too competitive with their emaciated offense this year but you never know.

  4. xoso888 says:

    Very good written information. It will be beneficial to everyone who usess it,
    as well as me. Keep up the good work – for sure i will check out more posts.

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