How do the Yankees value Justus Sheffield?

Prospect lists are ever-changing, as players graduate to the majors or fall because of injury or an inability to adjust to a higher level of competition. For the Yankees, this is borne out in in 2018 as their top-ranked farm system has seen two graduations: Gleyber Torres and Miguel Andujar. Their prospect status is rapidly eroding with every at bat, and that means someone else has to take over at the top of the rankings. With Estevan Florial out with injury, in the near term that top prospect may be the left-handed Justus Sheffield.

Since being traded from Cleveland in the Andrew Miller deal, Sheffield has rapidly climbed the ranks of Yankee pitching prospects, and has found himself some success in Triple-A. He’s had a very interesting 2018, with a 3.80 ERA to start the year after his promotion from Trenton. There are real concerns about him, though, and real questions about what he represents to the Yankees.

My favorite metric for pitchers is K-BB%, since it shows both an ability to hit the strike zone with consistency and the ability to fool hitters. Throwing strikes isn’t that useful if hitters can tee off on your stuff, but if you can’t throw strikes at all, you’ll never be a pitcher. Here’s a plot of MLB starters and their K-BB%, as well as tossing in Sheffield for comparison:

Sheffield sits way down the ranks as compared to MLB starters. Now, of course, he’s still a prospect and probably not ready yet for the big leagues. This data, however, suggests that maybe Sheffield is further from the majors than his Triple-A status would indicate.

Not to mention that his K-BB% has been decreasing consistently since 2016. Two straight years and multiple levels of the minors becomes a depressing trend pretty quickly, and maybe Justus just is too wild for the role a lot of scouts thought he could occupy.

The saving grace of his season so far has been contact, especially home run suppression. He’s surrendering just 0.42 HR/9, a sterling mark no matter the level. There’s concern there too, though, in that power is rapidly becoming the hardest tool to project in a prospect. Swing changes and a different baseball have revealed more power in a lot of players than we previously thought was possible. Gleyber Torres, Jose Ramirez and Francisco Lindor are prime examples of that. If low-power prospects can discover a home run stroke upon promotion to the majors, what’s to say that it can’t work the opposite way?

These concerns about Sheffield come right around the time that the Yankees have to make a decision regarding their starting rotation. There’s a hole that needs to be filled, and the Yankees have the pieces to make a serious splash at the trade deadline. Should they decide to fill the rotation with a Tyson Ross type, it may only require cashing in a couple of the B-level prospects in the system. For a big-name starter, however, multiple of the elite prospects will need to be dealt. Keep in mind that both Yoan Moncada AND Michael Kopech were needed in the Chris Sale trade.

That, then, casts a bright spotlight on Sheffield’s performance. As a 30th-or-so ranked prospect at the beginning of the season, he could well slide in to a deal for a top-end starter. That would involve the Yankees believing that the present value of a new starter’s wins is greater than the future value of Sheffield’s, and with some serious concerns about his progress in the minors, it’s hard to find fault with that belief.