Hooper has been doing a free fall down draft boards the last month or so, but he was discussed in a few mock drafts for the Phillies pick, so he's worth a look. Hooper is a 6'7" 230 lb LHP from De La Salle High School in San Ramon, CA with a College commitment to UCLA. He throws a 4-Seam Fastball that has been up to 97 mph, a 2-Seam Fastball with good movement that tends to sit in the 89-92 mph range, a Curveball he throws in the 74-78 range and a Changeup that needs a whole lot of work. So let's talk Pitches.
We'll start with his weakest offering, the changeup. Hooper's changeup is pretty bad, though that isn't unusual for a high schooler who can hit the mid-upper 90's. Most of you peers can't catch up to your Fastball, so there's no real need for the changeup and not much opportunity to throw it and work on it. Hooper reportedly threw a few good Changeups last Summer, but the problem is inconsistency (about to be a theme here). The best outcome is probably an average pitch.
His Curveball is a better pitch currently and could top out as a Plus pitch. He throws it mid-70's now, but as he adds strength it should creep up a few miles an hour, get stronger break and, possibly, more consistency. The pitch has two-plane break thanks to a 3/4 delivery (usually a bad thing for a Curve, but when you're 6'7" you can get away with it). The pitch is currently a below average offering, so there's a good bit of projection to the ceiling.
His four-seam fastball is currently his most impressive offering as it has unusually good movement for a 4-seamer and he can pitch it up to 97 mph and typically works 92-94 mph. There are 2 problems with the pitch. The first is stamina. In a single inning appearance last year on the showcase circuit he was able to throw 96 and 97 mph 4-seamers, but in longer appearances he doesn't have the stamina to get up to that. The second item is somewhat related: Consistency. As he gets tired this gets affected as well, though even in short appearances his mechanical consistency gets pretty wonky.
Lastly there's Hooper's 2-Seam Fastball another potential Plus offering. Hooper is comfortable working in the 88-92 mph range with the pitch. The Pitch has good late movement, but again it's inconsistent.
Now let's look at a video and talk mechanics. The first thing I notice in his mechanics is his landing foot, which finishes facing towards the left batter's box. This will tend to pull his pitches that way and also causes him to throw across his body which can add stress, limit your velocity and, on the plus side, does add deception to your delivery by hiding the ball for longer. The crazy thing I noticed next is that not once does hit the Catcher's target. His arm slot dances around a little along with his release point leaving balls high and pulling things to far across the plate.
The plus side is that you can see the movement on his stuff and it's easy to see the potential if you can harness that stuff. The problem is Pitchers beyond 6'5" tend to have very inconsistent mechanics. Those long limbs mean that being off just fractions of a degree can lead to big differences in distance of release point. The potential is a #3 Starter, the floor is Phillipe Aumont. Personally I would want nothing to do with Hooper, as the mechanical issues are very difficult to resolve and often when they do it's a very long development cycle.