Build: Tall, skinny, lanky build, yet athletic; Probably a bit heavier than 160 as listed; long arms; looks strong despite lack of weight
Mechanics: High closed leg kick; able to get knee to letters of uniform; stays closed and hides the ball very well; shows back numbers to the hitter creating deception; pitches from right side of rubber; short angled/across body stride to plate; lacks drive off mound; lands very closed and hard; forceful rotation with torso when throwing; stays stiff with upper half and arm; comes through with low/mid 3/4 slot; wrist has tendency to drop and get underneath ball. Mechanically he has a hard time repeating and being consistent and doesn't get to consistent release point.
Fastball command is a bit erratic but gets away with a lot due to deceptive mechanics. Ball is very hard to pick up out of hand especially to left handed hitters which appears to start behind their head. Great late life for his sitting velo; velo appears much harder and is apparent due to hitters' late reactions. Doesn't create a steep plane with fastball but angle of release point is awkward and out of the norm for hitters that it creates problems for hitters' visualization.
Breaking ball seems to be more of a slurve than a definitive curveball or slider. Mixes speeds with breaking ball well keeping hitters off balance; Harder slider creates difficult angle for left handed hitters (starts behind hitters) and they bail early. Did not use it as an out pitch for lefties though instead used fastball. Confidence may be lacking in pitch. Rolled a few curveballs over plate and seemed to lack conviction and finish on some breaking balls. More confidence and execution could make this a plus pitch.
Showed inconsistency and lack of command with changeup. Seemed to aim pitch and lack fastball arm speed. Slowed down mechanically when throwing CH and telegraphed pitch. Many CH were left armside high and not finished. This shows a lack of confidence in pitch. CH speed too similar to FB speed and lacks polish.
The youth of Josh Hader is a great thing. There is a lot of upside with him and the tools he possesses. His track record shows that he can get the job done and is doing so this year as well. Moving forward, his command of fastball and development of offspeed pitches must progress. However, this only comes with experience and more hours spent refining mechanics and repetoire in bullpen sessions. He has a great tenacity out on the mound and a very good command of the game for his age. He mixes pickoffs well to first with different looks. He is slow for his release time (1.41-1.90) but for a lefty that's not too worrisome. I'd like to see him throw fewer pitches per inning and learn to attack the zone early. He has the type of fastball where he doesn't need to pick the corners, he can throw it middle and let his sharp angles and deception do the work. He will need to create some repeatability mechanically but that always comes with age. Working at a slower more controlled tempo and creating more drive off backside would allow for better command of pitches. Overall, Hader looks like your typical late inning or lefty/lefty situational guy. With his angles and makeup MLB bullpen is definitely projectable.