Kopech came into the Fall League as one of the fresher young arms, having not thrown a competitive pitch until June 17 after fracturing his hand in early March, and then missing a week in July with a calf strain which combined to limit his season to just 11 starts and 52 innings at High A Carolina. His results for the year were a story of binary outcomes, with a late season surge of three consecutive starts where he threw 18 innings and punched out 32 while walking just four, and finishing the year with back-to-back starts of 0.2 and 2.1 innings, where he gave up six hits and seven walks combined.
His first AFL start on October 15 showed he’s got some gas left in the tank this year, as the big righty threw up three hitless frames, striking out five, and challenging hitters with great command of his fastball, sitting 97-to-99 mph (T100) and exploding in the zone with some slight arm-side movement. He pounded the zone to all quadrants, but with particularly sharp command to the glove side. Establishing the fastball to the outside corner to RHH played up a slider that had plus action at 85-to-88 mph, which he showed that he could vary the break on for a strike-throwing version with tilt and sharp bite, and dial-up some strike-to-ball sweep for swing and miss and put-away. The FB/SL combo, in this view, was dominant, with the hardest hit ball being a routine fly to left-center field. He also threw two changeups that flashed some late bottom in the 88-to-89 mph range that replicated the fastball arm speed of out of hand, though it was underutilized (and not needed) in this view thanks to the overpowering FB/SL combination. Overall he threw 40 pitches, 32 for strikes, with half of those balls being of the nibbling fastballs and hard slider-types to try to get some chase.
While his mechanics are high effort affair, they were repeated consistently in this look. He’s got a high leg lift and medium arm circle, showing the ball in the back, with strong drive off the rubber and a fast arm speed that comes violently through his 3/4s slot. His momentum carries his right foot over to the first base side when he follows through. He’s got the athleticism to make those moving parts work in sync at that tempo, and one evaluator I spoke with said those mechanics were actually smoothed out when compared to viewings shortly after the All-Star break, which is probably the best explanation for why his fastball sits in a more comfortable range – albeit still big velo – with better command presently. It also shows he is listening to his coaches, and making the necessary adjustments to get better, which is critical for any 20-year-old prospect. But what stands out to me most about Kopech is his developing build – he is clearly playing above his listed weight of 205 pounds. He looks much closer to 225, and his baggy uniform hides a large frame and sculpted upper body with broad shoulders, muscled arms and a strong lower half.
At just 20 years old, there is still plenty of risk in the profile, but there’s a lot to dream on with this kid’s raw stuff. This viewing certainly backs up the Red Sox’ excitement about his future potential, which I see as a solid Role 60, #3 starter who could reach a Role 70 ceiling if the command comes around to be at least average. It’s easy to forget that Kopech as has yet to pitch a full season of pro ball, and he’s totaled just 135 innings as a pro, but the ingredients are there, and durability, consistent mechanics, and improved control, especially of the fastball, are the benchmarks from here to throttle up his development.