The little guy out of Georgia got his first AFL action today, and in so doing also got his first exposure to PITCHfx. Of the 20 pitches he threw, 19 were detected, and here's what he flashed:
pfx corresponding to horizontal movement and pfz corresponding to vertical movement, as usual.
Fields was as advertised, a power righty with a fastball that gets into the mid-90s and a strong curve that he'll throw in any count. Nothing in there comes as a surprise. What's interesting to note is that, at least this afternoon, his pitches didn't have much horizontal movement. You'll see a lot of righty fastballs range between -4 and -10 and a lot of righty curveballs range between +3 and +8 (or so). Fields, however, stayed closer to zero, working mostly on the up-down plane and not throwing a lot of tail. (Remember that the numbers refer to deviation, in inches, from a pitch thrown with no spin, and that a negative pfx means the pitch tailed in to righty hitters and away from lefties.)
This shouldn't necessarily come as a surprise, either - it's a function of Fields' arm slot. It's just neat to see it in numbers. Where a lot of guys throw three-quarters and some prefer to drop down, Fields is one of those pure overhand guys, a guy who throws on top of his shoulder and unleashes his stuff on a downward plane, or at least as much of a downward plane as a little person like Fields can manage. When you throw over the top, it's difficult to generate the sort of spin necessary to make balls break left or right. So Fields gets by with a hard and literally almost straight fastball and a curve that travels along a similar path before breaking off the table. Read that sentence over again and you can see what makes him so tricky to hit.
Another thing to consider about Fields' arm slot - remember how Sean Green had a lot of trouble against lefties? Green threw from a sidearm slot that confounded righties but gave lefties a good look at the ball. The slot also wasn't conducive to generating good movement against opposite-handed hitters. By coming over the top, though, Fields should be somewhat immune to exaggerated splits, being similarly effective against righties and lefties alike. He probably won't slaughter righties the way some specialists do, but by not having the splits/exposure problem of many of his brethren, it's easy to see why he's always been considered a future closer. He has the stuff and mechanics such that he shouldn't have to pitch around any batter*, no matter on which side of the plate he's standing.
* if he learns to throw strikes