Evaluating the Prospect in the James Shields Trade

The only prospect involved in the White Sox and Padres deal for James Shields is 17 year old INF Fernando Tatis, Jr., who the White Sox signed during the 2015-2016 July 2 International Free Agent period for $700,000. Tatis was not ranked among the 47 prospects to which former FanGraphs writer Kiley McDaniel ascribed hierarchy on his 2015 J2 Sortable Board and was not on my top 10 International Prospects list from that time. He’s blown up a bit this Spring and is one of the more interesting bats in Extended Spring Training.

As an amateur, Tatis lacked physicality. He was clearly underdeveloped compared to his peers, and was bereft of the bat control and strength in his hands that are required to really drive pitches in various parts of the strike zone, especially for a prospect that profiled, at the time, as a likely corner infielder. Tatis’ frame had projection though, and a rather significant amount of it considering his age and bloodlines (Fernando, Sr. had one of those jean-selling bodies in his prime).

The Fernando Tatis, Jr. we’ve seen here in Arizona for Extended Spring Training looks very different. Tatis has already made significant physical progress — the only video I have of Tatis right now is his at-bat against Brady Aiken from last week, which starts at about the 2:00 mark, but you can at least get a look at him singling there — and it’s made a huge difference in his overall play.

He has displayed improved control of his body, is making a higher quality of contact and has just generally become explosive enough that the sentiment among evaluators out here is that Tatis has a solid shot to remain a shortstop. His routes to ground balls, his hands and actions have all been good and project to be of Major League shortstop quality and he has a plus arm. He’s currently an average runner, which will be fine for short if he can maintain that speed, but of course at just age 17 he’s going to keep growing and probably slow down some.

While he can play there for now, the chances of Tatis remaining there in his prime are somewhere between “moderate” and “unlikely” on the Continuum of Shortstopdom. Should he have to move it will likely be to third base where, given those shortstop-quality actions, his glove would arguably project as plus.

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Even since just the early part of Spring Training, Tatis has improved his footwork in the box, is tracking pitches better and using the entire field. He still hasn’t displayed the kind of wrist/hand strength that’s indicative of impact power and he really only projects to have about average pop at maturity, but if he can stay at shortstop that’s going to be just fine. The bat projects to average as well. A 50/50 hit and power combination from a shortstop, even one that is just passable defensively as Tatis would likely be, is value on par with an average regular. Given Tatis’ age and proximity to the Major Leagues, there’s obviously a substantial amount of risk here, which suppresses the Future Value grade below.

Hit: 20/50, Raw Power: 40/50, Game Power: 20/50, Run: 50/45, Field: 40/45, Throw: 60/60, FV: 40

The other return on the deal is 26 year old RHP Erik Johnson. Johnson’s four pitch mix — fastball, slider, changeup, curveball — is mediocre. He’s experienced fluctuations in velocity during each of his abbreviated big league stints and this year the stuff is down. Johnson has been about 89-92 this year with below average control that often leaves his fastball either in the top half of the strike zone or out of it altogether.

His slider is above average, in the low-80s and Johnson finds his spot with it more regularly than the fastball. The changeup will flash above average from a pure movement standpoint but Johnson’s arm action is different on the change and big league hitters have been able to identify it. Because of this, Johnson deploys a back foot slider as his go-to weapon against lefties for swings and misses. His curveball sits in the low-70s and is a slower, deeper, more infrequently used change of pace used for early count strikes.

Johnson, who has been sent to Triple-A El Paso, gives San Diego an arm to run out there every fifth day for the rest of the season if they need it and doubles as a reclamation scratch-off ticket because of his interesting pedigree. PETCO Park should provide a bit of a cushion should Johnson fall into San Diego’s rotation.





Eric Longenhagen is from Catasauqua, PA and currently lives in Tempe, AZ. He spent four years working for the Phillies Triple-A affiliate, two with Baseball Info Solutions and two contributing to prospect coverage at ESPN.com. Previous work can also be found at Sports On Earth, CrashburnAlley and Prospect Insider.

17 Comments
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ryanMember since 2025
10 years ago

I see this statement a lot and its really frustrating.

“He’s currently an average runner, which will be fine for short if he can maintain that speed, but of course at just age 17 he’s going to keep growing and probably slow down some.”

Why is it there is this belief that baseballs players will get slower from when they are 17-18 years old? Players should be able to add speed up until they are 23-24 years old which is the usual peak age for speed.

Just because players add weight and muscle mass does not mean they slow down.

ryanMember since 2025
10 years ago

Mike Trout was pretty fast at 22 and I would say he was faster at 22 and 23 than he was at 17, wouldn’t you? I didn’t mean my post to sound like an absolute but I just don’t like when I hear this player will slow down when the player is only 17 or 18 as there is lots of room for him to get faster.

JoserMember since 2021
10 years ago
Reply to  ryan

Sprinters can get faster as they add muscle, because they’re training as sprinters and the muscle gets added where it makes them faster. Baseball players aren’t training as sprinters (at least, not primarily let alone exclusively) so they’re going to tend to add muscle in the upper half where it helps with swinging the bat but does nothing for running except adding weight for their legs to carry around.

RonnieDobbs
10 years ago
Reply to  ryan

Joser says it well below. Baseball players do not get faster. They get bigger and softer as they age. In theory, they could but they don’t train that way.

mattMember since 2023
10 years ago

Is the up vote/down vote system new? Didn’t see the thumbs before.

Promising write-up, rather take a chance on Tatis jr than get one of there than get one of their upper level guys like Hawkins, Danish, Beck who seem like low ceiling prospects (yes I know about Hawkins past but he’s not going to suddenly stop swinging and missing) with high risk.

RoyalsFan#14321Member since 2020
10 years ago

I often wonder if in the cases of prospects like Tatis Jr if he gets too much credit for having a father who played (with some interesting success) at the major league level. I would love to see a study about how prospects are rated relative to having fathers with major league success. Raul Mondesi, Jr is another example of this, in my opinion.

JediHoyer
10 years ago

Mondesi overrated? 20 y.o ss with pop, speed and plus d?

mattMember since 2023
10 years ago
Reply to  JediHoyer

I thought headed into this year Mondesi was overrated, he had a very low BB%, struckout a lot, and power for a young guy in AA was decent but he had never had an ISO over 150, and yes I realize his age but continuing to put him on top 25 lists was silly imo. He was very good till his suspension, will be interesting to see what he does when coming back and if the power spike continues.

JediHoyer
10 years ago
Reply to  matt

I mean he doesn’t even really need a ton of power. Plus speed and d at short and hitting 10% lower than average is like a 3-4 win player.

mattMember since 2023
10 years ago

I think it’s been proven in studies in past that bloodlines do help. But I think it’s not fair if you are stating that Eric is overrating this prospect based on that. He stated in the article what he likes about his game. And nobody is going to rank a prospect top 30 on international list and given 700 K (which I believe a article said some scouts think that was a bargain) on bloodlines.

jlongrc
10 years ago

Johnson is a mystery to me. At one point, at the AAA level, he had excellent control. He also had a hard, 92-95mph (touching 98 here and there) fastball though it was and is very straight. His slider looked great. Then he got his shot in the majors and lost a lot of velocity, couldn’t buy a strike, and just never looked like the same guy again. I believe it may have been FG that wrote about him changing his mechanics the next season, but I still see him as a guy who may have a sneaky repetitive motion injury a la labrum.

kahlmyishmael
10 years ago

Didn’t Maury Wills get better at running the bases as he aged and got older?

rosen380
10 years ago
Reply to  kahlmyishmael

Getting better at running bases can happen even with plateau’ed or declining speed, if the player is getting smarter at getting leads and reading pitchers and such.

Wills made his debut at age 26, so not sure he’s a good player to look at as far as how fast teens age in the speed department; that said his three-season average BsR/600PA:

26 2.8
27 6.6
28 5.3
29 6.3
30 3.9
31 3.2
32 2.7
33 1.6
34 1.9
35 1.4
36 0.4

And that late 20s bump seems to be pretty heavily influenced by what appears to be a base running outlier for Wills in 1962.

TKDCMember since 2016
10 years ago

Unfortunately, Chan Ho Park only had daughters.

LHPSU
10 years ago
Reply to  TKDC

Well, if there’s a position that women have a chance of breaking into men’s baseball as, it would be pitcher.

Alex87878
10 years ago

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