Going Deep: Is Ji-Man Choi The Rays Best Power Hitter?

It happens every single year without fail. An unknown, relatively unheralded prospect gets signed and proceeds to tear his way through the lower minor leagues and starts to make a name for himself. People start to get really excited but then before you know it, just as quickly as it started the meteoric rise is derailed, sometimes by injury, sometimes by suspension, sometimes both. The player’s career stalls at AA or AAA for a few years as the player gets back on track, maybe get a cup of coffee or two.  Suddenly that player is heading into the back end of their 20s and they’re just now getting their first real shot. Even though they do well and make big changes to their approach, whether due to their age, or the sample size, or lack of pedigree, their performance ends up going relatively unnoticed by the industry at large. Max Muncy, Justin Turner, Jose Bautista, Mitch Haniger, Jose Martinez, Joey Wendle, and Whit Merrifield are just a few of the impact fantasy hitters to emerge over the last few years who didn’t really get their start until their late 20s. In 2018 one particular hitter took this path to the big leagues and due to a steroid suspension and a broken fibula didn’t get his first real taste of big leagues until he was 28 years old. Despite putting up big numbers over the second half of the season, this player is going largely unnoticed so far in drafts this year.  I think this is an oversight on our part, and merits further exploration. First, though I would like to do a quick comparison of the peripheral stats of two different players from the 2018 season.

BB% K% ISO wOBA wRC+ HR/FB% AVG Launch Angle AVG Exit Velo BBL%
Player A 11.8% 24.9% .242 .367 135 20.8% 13.6 90.0 11.7%
Player B 13.2% 24.9% .204 .342 120 19.7% 11.9 87.9 9.5%

Those two profiles are so close to each other I’d probably be able to convince you that they were just two different seasons by the same player. That would a dirty rotten trick though and I would never do that to you (I say while batting innocent looking eyes at you). Seriously though, I promise this is two different players. Based on their elite ISO, and HR/FB% numbers we’re clearly talking about two sluggers who hit the ball hard and in the air (check out those launch angles and exit velocities) while squaring the ball up at a rate well above the league average BBL% of 6.1%. They both were well above replacement level hitters based on both wRC+ (100 wRC+ is average) and by wOBA (.340 is the baseline) and each player demonstrated an excellent eye at the plate as evidenced by their elite BB%. If you haven’t already guessed from the title of the article (you cheater you!) Player A is the Rays DH and First Baseman Ji-Man Choi. Player B, on the other hand, is a darling of the fantasy baseball community (myself included) and is expected to have a big year for the Mets in 2019. That’s right Player B is the Metropolitans young stud Outfielder Michael Conforto. For the record let’s take a look at where both players are currently being drafted in NFBC Draft Champion drafts.

Michael Conforto 102
Ji-Man Choi 493

How crazy is that? Throughout this article, I’m going to compare these two players and a few others in order to show that while we absolutely should be excited for Conforto’s 2019 I think that based on how similar they are as hitters we should be equally intrigued by what the year can hold for Choi as well.

Now we’ll get back to Conforto but now let’s put him aside for a moment (nobody puts Michael in a corner!) and focus on Choi for a moment. Choi began 2018 in the Brewers’ AAA system where he was brought up a couple of times to fill in the gaps but didn’t end up accumulating more than 30 at-bats in Milwaukee before he was traded on June 10th, 2018 to the Rays for Brad Miller and cash. A month later on July 10th, he was brought up from AAA by the Rays and never looked back. So far Choi had not shown much in the majors but the moment he set foot in Tropicana Field everything seemed to fall into place for him. The Rays hold a reputation as one of the biggest proponents of the fly ball revolution and you could see the effects almost immediately in both his statcast data and the results that followed. Let’s compare his underlying stats from before he came to St. Pete to what he has managed to put up so far in his Rays tenure:

Time PA wOBA .ISO HR/FB% .AVG BABIP BB% K% Launch Angle Exit Velocity BBL% 2B/PA
Before 7/10/2018 179 .291 .217 20.3 .191 .202 12.7% 25.7% 10.9 89.9 6.4 25.6
After 7/10/2018 189 .375 .269 19.0 .269 .310 12.7% 21.7% 12.7 89.7 10.9 15.8
Full 2018 Season 368 .364 .242 20.8 .263 .315 11.8% 24.9% 13.6 90.0 11.7% 15.8

It’s like looking at two totally different players. Now I don’t claim to be a swing expert (I just play one on TV) but it appears that by raising his launch angle nearly two degrees Choi completely revamped the quality of contact that he was getting. His wOBA jumped nearly 80 points, and his .ISO followed it up by gaining 52 points while his BBL% went through the roof. If there ever was a poster child for what launch angle can do for a hitter Choi is it. Now, of course, the question is just how legit is this leap? With such a huge leap in BABIP was it all just smoke and mirrors or legitimate growth? It’s hard to tell in such a small sample but let’s take a look at what xStats has to say about the legitimacy of his numbers from last year:

2018 Actual 50.0 .263 14.0 10.0 .358 .505 .369 .365
2018 xStats 48.6 .256 12.4 9.8 .351 .487 .360 .355

I honestly don’t even know if I’ve ever seen a player’s actual stats and their xStats line up so perfectly. Based on his batted ball data, Choi’s season was as legit as they come. It’s still a relatively small sample but what Choi did last year in his 221 at-bats was not the result of luck. That’s fantastic. I’m especially encouraged by that wOBA number. Anything above .340 is considered above average so you can understand why I’m excited about xStats backing up its validity.

How about Choi’s AAA stats? Perhaps an inspection of his minor league numbers might help add some additional heft to this small sample of success and perhaps even show a pathway to additional improvement. Let’s take the ratios and factors included in Mike Podhorzer’s incredible article on adjusting minor league stats to their big league equivalents and see how those minor league numbers compare to his numbers in Tampa.

2017 AAA 27 288 .288 25.4% 18.8% .373 .538 .394 149
2018 AAA (MIL) 28 129 .302 19.0% 11.8% .436 .488 .412 148
2018 AAA (TBR) 28 74 .270 20.9% 11.3% .360 .405 .347 119
2018 AAA Total 28 203 .291 19.7% 11.5% .410 .458 .385
2018 AAA Adjusted 28 203 .278 20.8% 16.2% .398 .470
2018 MLB TBR 28 189 .269 21.7% 19.0% .370 .506 .375 141

Check out the AAA adjusted line. They match up pretty darn well. Based on this data, it seems reasonable to draw the conclusion that we’re actually talking about a 409 PA sample. That’s pretty much 2/3rds of a full season’s worth of plate appearances. Suddenly this is starting to look like genuine growth as opposed to a fluke occurrence. Not to mention there might even be some room still f0r improvement with regards to his AVG given his minor league track record. Heck, we’ve made bigger leaps with regards to potential in similar samples.  Adalberto Mondesi only put up 291 plate appearances of improvement last year and you’re seeing him in the top ten rounds this year. The year before Matt Olson went on his home run binge in only 216 plate appearances and we were drafting him last year in the tenth round on average. Choi, on the other hand, is pretty much free at this point.

Okay so now that we’ve taken a look at Choi’s season let us bring Conforto back into the picture (welcome back Mike!) Let’s take another look at that comparison between Conforto and Choi’s 2018 seasons.

Conforto .243 .204 13.2% 24.9% 19.7% .342 120 .448
Choi .263 .242 11.8% 24.9% 20.8% .367 135 .503

As I said before there’s a ton of similarities in how their season’s played out but we all remember Conforto’s breakout 2017 right?  That’s the real test. Let’s compare that season to Choi’s 2018.

Conforto 2017 .279 .276 13.0% 25.7% 27.3% .392 147 .555
Choi 2018 .263 .242 11.8% 24.9% 20.8% .367 135 .503

If we were looking for a poor man’s 2017 Conforto I think we have found him. Honestly, I think there might even be room for the gap between them to close even more. I initially stumbled upon this Conforto comparison when I searched for players who matched Choi’s BBL%, Average Exit Velocity, and Average Launch Angle. Both are really useful stats, especially for finding yearly swing changes or batting approach but they can be a bit misleading for exact power potential.

Instead, I like to take a look at StatCast’s xISO stat in their search database, which uses launch angle and exit velocity to determine what the expected ISO of a hit should be. I then set the threshold at .200 (since this is roughly considered an elite hit power wise), and count up how many of these balls they hit. I call these hits Expected Elite Power Hits, aka exEPH. I find exEPH to helpful because it helps me separate the power quality of the player’s contact from the results.  For example, say a player hits a double. That double can be the result of how well hit the ball is for sure but it could also be the result of the fielder taking a bad route to the ball, or hustle on the hitters part. It can also go the other way.  Imagine the same hitter crushes a ball into the gap but he’s facing the Rays and so Kevin Kiermier comes sprinting over and makes a spectacular play to take it away. It was a great hit, fielder just made an even better play.  My hope is the exEPH removes the chaos and let us know a hitter’s true power potential. I’ve also thrown in what percent of their pitches seen they hit for xEPH. Finally, I like to add in the average and medians for the exit velocity and launch angle for their home runs. Please note that these numbers are more meant to compare player profiles as opposed to seeing their value as a power hitter in a vacuum. So let’s see how they match up.

Player # of Pitches Percent of Pitches hit for exEPH # of exEPH Av EV of HR Med EV of HR Av LA of HR Med LA of HR
Conforto 2017 1828 4,2% 77 104.0 103.5 28.0 26.0
Choi 2018 917 4.0% 37 104.1 105.0 29.1 29.0

Keep in mind we’re comparing Choi’s 2018 with Conforto’s breakout year back in 2017. The power profiles are practically identical. By the way, if you extrapolate Choi’s xEPH numbers over Conforto’s pitch count you end up with roughly 74 xEPH hits. We loved Conforto’s power potential coming out of 2017 and seeing how closely the profiles line up I just can’t see a reason why we shouldn’t be excited about Choi in 2019.

If you’ve read any of my other Going Deep player profiles you’ll know that I usually like to wrap things up by projecting a range of outcomes. We started the article with what Choi’s stats would look like if you prorated them over 600 PA. To save you scrolling back in forth here those numbers are again for reference. I know I have a tendency to talk too much about roto big picture so included walk, strikeout and doubles totals for you points league folks!

.263 27 67 86 5 71 149 38

Now that would be a season, now wouldn’t?  Now, of course, I don’t expect those exact results but it certainly gives us an idea of what he is capable of a true peak season.  Let’s make a few more season-long comparisons just for perspective.

Mike Moustakas .251 28 66 95 4 49 103 33 158


Matt Olson ..247 29 85 84 2 70 163 33 106


Justin Upton .257 30 80 85 8 64 18 96


Stephen Piscotty .267 27 78 88 2 42 114 41 155


Cody Bellinger .260 25 84 76 14 69 151 28 44

While we’ve been spending most of our time with the Conforto comparison (rightfully) if I’m being honest I think Mike Moustakas and Stephen Piscotty’s seasons are good markers for what kind of fantasy value Choi’s ceiling might hold in 2019. Given his minor league track record, I could even see a bump up in AVG to around .270-.275 but I’m not going to expect it either. Here’s my reasonable expectation for his highest ceiling.

Choi’s Ceiling .270 29 75 85 5 75 103 40

Now, what about his floor? Obviously, it could crater. We only have a 221 plate appearance sample size to go off from last year so all of this improvement could simply be noise. With that being said the Rays have long had a track record of success with taking sluggers who needed some form of a launch angle adjustment (see Cron, C.J. or Morrison, Logan or Dickerson, Corey) so it’s perfectly fair to expect that power stick around to a certain degree no matter what. My biggest guess is that we perhaps see some of those potential home runs turn into doubles instead and a drop in batting average but given how hard he hits the ball I wouldn’t imagine too far of a drop. I think a reasonable floor given a full season of at-bats looks like this:

Choi’s Floor .250 22 60 75 4 60 120 35

Obviously, he could lose the starting DH role but I don’t think analyzing that is useful to us here, also the Rays have said the job is his to lose and he should see games at first base as well. I’ll admit that isn’t exactly a particularly inspiring fantasy line but given that Choi is currently going at pick #492 in NFBC drafts the risk is pretty much nothing. If this is what he puts up it costs you pretty much nothing on draft day so there’s almost no risk. Just like with his ceiling let’s make a few comparisons again.

Yonder Alonso .250 23 64 83 0 51 123 19 293


Kyle Seager .232 22 62 78 2 38 138 36 232


Jed Lowrie .267 23 78 99 0 78 128 37 266


Justin Smoak .242 25 67 77 0 83 156 34 225


Asdrubal Cabrera .262 23 68 75 0 41 119 36 264

I think all of these players are solid comparisons for Choi’s floor, especially Justin Smoak. Note that ADP on Smoak. He’s currently going in the 19th round! You can get Choi, who is in a way better offense and whose floor matches Smoak’s ceiling, over 200 picks later! Given that Choi’s BB% is so much higher than most of the other comparisons I’d say he’s a steal over the non-Smoak hitters shown here.

So finally what do I, esteemed fantasy prognosticator, think Choi’s season is actually going to look like? As per usual somewhere in between his floor and his ceiling but honestly I lean more towards the ceiling. If you’re willing to include his AAA numbers in 2018 I believe in the power numbers and I feel that the Statcast, xStats and xEPH numbers back that up. I see the potential signs of the classic “hitter making a change in his approach and coming into his power” profile much like we saw Michael Conforto do in 2017. His elite walk rate is backed up by an above average O-Swing% of 23.4% meaning he doesn’t chase pitches combined with an average Z-Swing% and Z-Contact% which seems to indicate he picks his pitches in the zone and hits them when he does swing. Tampa is a middle of the pack offense but Roster Resource has him batting cleanup which should certainly help him put up good RBI numbers.  All of these factors make feel really bullish on Choi’s potential contributions in 2019. With all that given, here’s what I expect from Choi in 2019, along with where that would rank amongst First Baseman (where applicable) according to Steamer projections:

Choi Actual .268 (12th) 26 (10th – T) 70 (19th) 85 (8th) 5 (10th – T) 70 (14th) 110 36 (2nd)

For a guy going undrafted in most leagues, that’s a really solid First Base option.  It is worth noting in leagues with real strict position qualifications (I’m looking at you CBS) he might not qualify right away at first but the Rays have expressed that they expect him to fill in at first quite a bit and reports are that he’s looked good there so far this Spring so I expect he will get that eligibility pretty early on in leagues where he doesn’t already qualify. I suspect that if he is given a full season’s worth of plate appearances that Choi will have a real shot at finishing as a Top 20 First Baseman if not as high as in the top 15.  That’s the kind of pick that usually goes in the top 150 to 200 picks, while you can get Choi at a near 300 pick discount. How can you say no to that?

Graphic by Justin Paradis

Daniel Port

Daniel is a Fantasy Baseball writer, Brewer, and Theatrical Technician, located in Denver, Colorado. A lifelong fan of baseball and the Cleveland Indians since before Albert Belle tried to murder Fernando Vina, he used to tell his Mom he loved her using Sammy Sosa's home run salute, has a perfectly reasonable amount of love for Joey Votto and believes everything in life should be announced using bat flips. If you want to talk baseball, beer, or really anything at all you can find him on twitter at @DanielJPort !



Michael Berney

Daniel: fascinating article. Can you forecast what will happen if Choi actually gets 600 plate appearances and 200 of them are vs LHP? Does that greatly reduce his his expected value?

Daniel Port

Hi Michael! Thanks so much for reading and for the kind words! If he did get a full 600 PA with 200 coming against lefties I wouldn’t necessarily expect a large change in his power numbers in a vacuum. Mostly we’ll see a drop in AVG and maybe a few more home runs just because of volume. I think you could expect a .240 to .250 AVG with 27 to 28 HRs with a few more runs and RBIs again mostly as a result of the aforementioned volume. It’s not entirely out of the question that gets closer to that than expected the Rays have already said the DH job is his to lose and so far his 1B defense has gotten rave reviews so he might see even more time there than expected.

Daniel Port

Hey Zach! Thanks for reading and for commenting! It’s entirely possible but given that Choi is getting pretty good reviews at 1st so far in ST I think that the opportunities will be there even if Diaz bumps into his playing time at DH a little bit. If anything I’d expect Diaz to mostly cut into time at 3rd especially given Matt Duffy’s health in general. I’m also not a huge believer in Diaz until I see that evidence that he genuinely has committed to making the launch angle adjustment he needs to really unlock his potential.


The fallacy here is that 168 of Choi’s 190 ABs were vs RHP!! Whereas Conforto has played pretty much everyday against samesiders too. Considering how extreme splits often are vs LHP, you dont think that figures in here? Also the high likelihood of Choi being platooned, whereas Smoak is a switch hitter (as I recall) and in any event plays every day …. and that makes Choi WAY more of a Daily league / DFS play that Smoak or Conforto. PT matters!

Daniel Port

Hey MC! Thanks so much for reading and weighing in. You are 100% correct PT definitely matters. It matters a lot. At the rate that the Rays played Choi last year would have played in roughly 120 games but when you break it down month to month the number of games he played in increased each month from 66% to 70% to 71.5% and that’s before you factor in that he missed 6 games in September which could have potentially bumped that last % as high as 82%. That puts him alot closer to 133 games or 475+ PA. Throw in that he’ll be playing at either 1B or DH and there’s really only three candidates for the job I don’t think it’s unreasonable to put 450 PA as a floor but if he performs he could reach even higher PA numbers. In so far as daily leagues go, I think you couldn’t be more spot on, and in retrospect, as I have been trying to make an effort to address points league values a bit more, I should definitely do the same for daily leagues. In a daily league, I bump him up for a solid lottery ticket to must own as he just mashes righties. Also while Conforto and Smoak get more PAs facing lefties they probably shouldn’t as Conforto is a.215 hitter against lefties for his career and Smoak is a .235 hitter against them as well. I’m not sure I want to be playing those PA in that instance anyways. Either way you make some great points and I really appreciate your response!

Daniel Port

Hey Josh! Thanks for reading and for commenting! Nate Lowe should definitely factor in to some degree but he’s got to prove he’s ready in ST this year first. I wouldn’t be shocked either if there is some service time manipulation with Lowe in the beginning which can only work in Choi’s favor. He’s definitely one of the players I’ll be watching the most in ST to see how that shakes out because if he’s not ready there could be even more playing time in Choi’s future.

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