In a year where the rotation was troubled by every conceivable problem and worry imaginable, Indians rookie Zach Plesac was a pleasant surprise. While he wasn’t perfect by any stretch, likely outpaced by Aaron Civale for “Most Impressive Rookie Pitcher”, Plesac ate up 115 innings and offered a solid if unspectacular 3.81 ERA. With just 88 strikeouts and a 1.23 WHIP though, there’s worry that he may regress in some way. After all, when you don’t really do anything super spectacular as a rookie, or have some kind of weird skill or quality to hang your hat on, you eventually get figured out. In at least one sense though, Plesac stands in curious company.
On Baseball Savant, they have a player comparison tool. It uses affinity scores to give an erdos number that basically shows how similar a player is to another. The closer to 1 you are, the more similar, and the lower the decimal (.99 and descending) the less similar. For instance, the player most closely comparable to Mike Trout, with a .64 affinity score, is Yordan Álvarez, which speaks to the excellence of Trout and of Álvarez. Tommy Pham is Carlos Santana’s closest comp with a .82 affinity score. Read about it more here. It’s neat.
Anyway, in terms of velocity and pitch movement, Plesac has a few very interesting names that relate to him, because his velocity and pitch movement aren’t really anything to write home about. His closest relation is Taylor Clarke, a rookie for the Diamondbacks. There’s a few other pretty close ones, most names that don’t leap off the page for any good reason (Kyle Gibson at .94, Matt Harvey at .97), but with a .93 affinity score sits Indians newest ace, Shane Bieber.
This is simultaneously surprising and completely sense-making. Bieber is an amazing pitcher, an emerging star and if he continues to improve a strong Cy Young candidate for years to come. He doesn’t throw especially hard though, and while he gets amazing whiff rates on his slider — 40.7% slider whiff rate ranks 17th in baseball — it actually moves 3% less than the average slider vertically and an astounding 71 percent less horizontally. For such a young guy, he’s quickly mastering the true art of pitching, rather than merely overpowering his opponent. He is very much more than the sum of his parts.
That same equation doesn’t quite add up the same for Plesac. He simply isn’t the artist that Bieber is right now. He actually has a lower hard-hit rate than Bieber — 38.7% versus 43.1 for Bieber — and 40.2% of his pitches are on the edge of the plate, similar to Bieber’s own 41 percent. Problem is, he also throws the ball in the heart of the plate, the place where it’s easy to hit it, 29.5% of the time, compared to Bieber at 23.8%.
That’s what separates Bieber and Plesac. Their sheer stuff is quite similar, and both do pound the zone in some wat or other, but Plesac has never really demonstrated the location skills that Bieber has been doing since he was a minor leaguer. When the stuff itself is merely solid, this borderline intangible is all that makes Bieber a monster. Which also raises questions about his own longevity, if one of those pitches doesn’t make a Kluber Slurve or Rivera Cutter kind of jump.
What to make of Plesac then? Throwing strikes is of course important, but just chucking it in there is a fool’s errand. He needs to get better, that’s all, find a way to either baffle hitters or blow them away. Right now he’s shown he has the tools right now to be a younger, maybe slightly better Adam Plutko. That's still a useful piece, but with the recent history of Cleveland pulling borderline aces out of its organizational butt you’d hope there’s more to him than just that, some kind of pitching blood they can squeeze from that stone. If the 2019 season is all that Plesac has as his fifteen minutes of fame in his major league career, so be it. In all honesty, he didn’t show anything this year to make us hope for anything more than merely okay.
The magic of the rookie, the tantalizing excitement, is in the what if. That’s what Plesac has going for him, whether he pulls an Ottovino and develops a new pitch or refines his mechanics to the point where he’s Bieber Junior. He has an affinity for Bieber’s raw stuff, it’s just the little extra something that makes the star from the raw material. Plesac’s Major League life so far has been charmed by luck, he has to make his own when 2020 dawns.